Does anyone know what I saw ?

Three possible things.

1) if the wire just happened to be near an output cable, and actually was a zip cord 12V cable to turn on other items automatically. Auto turn on is a common feature that a preamp would have what looks like zip cord coming out of the back...

2) a ground problem solution. Inelegant, but possible.

3) rather esoteric: a tweak where the negative or ground side of a device has an added pigtail of wire to 'enhance' the sound. This seems an odd impimentation of it, but with tweaks of this sort, anything is possible. And yes, the pigtail of wire on a ground/negative side works. Why?? I have not got a clue, but i have them on my stuff and they definitely add clarity and better dynamics. For speakers I add a ferrite at the end of the wire stub.
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4) the preamp was so anemic it needed a transfusion. So a 'donor' preamp was feeding it some juice to keep it 'alive' until someone bought it. Then the excuses would start as to how it just needs to 'break in'..
(8^Q...

This was years ago, and it was an ARC LS2, so not too anemic and never to be confused with a Bose product.

Elizabeth, I think item #3 is the closest. These were speaker lamp cables spliced into the preamp outputs (one each channel). It was some type of audio store tweek that they don't want you to know about. That is what I suspect (The dark side of audio sales) that makes things sound better than they will in your system.

Could you please expand more on the pigtail tweek? It sounds interesting and something I have never heard of.
Were do you suppose the cables went to? Ithought they may goto a subwoofer too?

The 'pigtail tweak' is a simple wire, group of wires, wire to bulb of metal at end of wire. not grounded (not stuck to anyplace the metal has other contact to be a connection to other wires, metal, except the ONE connection to the terminal. it is not part of a complete circuit).
The pigtail is placed only on the neutral side (of A/C wiring) or speaker level wires on negative terminal amp or speaker.
The wire is a few inches and has various calibrations, some have several smaller wires five inches long all together, others a wire with a termination. (I use the wire with termination of a ferrite. The ferrite I use is a 1" tall half inch diameter barrel with the wire end stripped and wrapped around the Ferrite, then teflon taped all over the assembly with the wire about 6" long out from ferrite. This is placed on any convenient spot (amp the terminals are five way posts, if using spades for speaker wires, stick on banana on negative terminals, or at speakers.For A/C outlets on neutral side only of other duplex outlet for amp, preamp...
The A/C one you MUST be certain it is on the neutral wire,and NOT on the hot wire!!!!!!!! (this can be hidden inside duplex box very easily, attaching the wire to the neutral duplex outlet. just make certain the stuff is well wrapped many layers of blue/pink/yellow teflon tape (the white tap can be used, it is just thin, and needs many more layers to be shieleded from direct contact if inside the receptical.
I have been thinking of trying some with tiny ferrit and very thin wire on signal level areas in electronics. At RCA out, inside equipment at negative RCA terminal...??
This tweak is totally at your own risk, especially on A/C!!! and if you are a putz, do not try these tweaks. they can if done wrong electocute you. destroy your equipment, start a fire.
As to why they work???
and for results, the results depend on so many factors...
I tried this tweak before and nothing. Then I have been upgrading, and adding other tweaks and now the pigtail tweak works really great for me. Better clarity, and better dynamics.
Special pigtails can be purchased for big buck$$$ or just get some wire and some small ferrite bits and make them yourself.
This tweak is discussed more over at audio asylum tweaks DIY forum.

Yes, something you do not want to know about as it will destroy your system. Elizabeth is leading you into audio hell.

Tweak Hell!!1 HAH Haaaaaaaa die tweaker die....(I AM already a souless alien using this zombie body to watch you humans self destruct!!! ..)
Hey, I could care less if you try or not. I am (unlike many posers here), NOT selling ANYTHING!)

These tweaks cost pennies (well maybe a buck) and can be useful. or not. then you're out a buck. Well, maybe two bucks if you made two of them...

See, THAT is the slippery slope to audiophile Hell!! Just a buck, well maybe two bucks.. pretty soon it's $14,000. at the drop of a hat to change what used to be done with a tone control... Hah hah ha...

Better than buying a new preamp for $14,000. and finding out it is exactly the same as you're old preamp.... Or worse. not as good!
So two bucks?... or... $14,000. Which would YOU try first?