venison stew left on the stove

You should toss it out. Chalk it up to experience, mistakes happen..you just dont want to compound it, this has stayed too long in the Danger Zone to be safe.
Here's a tip I utilize when making braises and soups that I know I will be storing. As part of your prep, put out two nested bowls. After dinner, fill the larger bowl with ice, water and a good shot of salt and stir to combine. Nestle the smaller bowl inside with your leftovers. As you cleanup, stir from time to time to aid in chilling it down. When your kitchen is in order, cover the leftover bowl and pop it in the fridge.

If it was on the heat and kept simmering it should be okay,maybe over braised but edible. If it wasn't on the heat the meat probably cooked down in the danger zone and went bad and i'd think it should be tossed.