Old school Specialized Hard Rock from
 

Have an old school hardrock from probably 1991. The left side top shifter (the smaller tab you click to bring the 3 speed down, i think I spring fell out of it and now you can't down shift it. Any ideas where to get this spring?

Hi Jackie, welcome aboard.

Its not quite that simple, we really need pics to try and help you and any marking on the part or the shifter on the other side especially if matching.

There were often many variations.

You can upload pics to the gallery on your home page and we can see them and move them here.

Springs don't normally get lost by themselves, they can break, get sticky or jammed and not catch or return but you would notice something broken or missing.

You could dribble some WD-40 into it and see if it frees up and starts working but go easy, it can get messy if you do. ;)

If that's the original set of shifters, you may be better served by getting a new set. You can grab a new set of Altus 3x8 shifters for about $30 and they work great. I just installed a set on the missus' recumbent.
As for the problem itself, is the shifter installed in the bike? Is there cable tension from the derailleur on it to pull it down to the smaller rings? Is the housing bent/corroded in any way that might impede the movement of the cable? Where has the bike been stored and what kind of weather conditions has it seen?

Both my pre-shock Hard Rocks have had shifters removed and replaced. I get all my parts second hand and they usually come with 2 tires, 2 rims, 2 pedals, 2 shifters, handle bar and stem, a seat post and maybe a seat for $5. And you get a frame too.