If you want to hold it then an amphibian is out of the question. There permeable skin will absorb the oils and contaminants on your skin, and can harm them.
So lizards... you could keep anoles, but they aren't much for handling. Most terrestrial geckos will do fine in that size tank... arboreal geckos need more vertical space to climb (and they suck for handling as well). Leopards, Bandeds, African Fat Tailed geckos are all great for handling, many of the other ground geckos can be a bit skittish. Sand Fish Skinks will also do fine in a tank that size. They aren't the prettiest and you won't see them much, but they are real neat critters (this coming from a snake person
). A Fire skink should do fine in a 20 long as well. Emerald Swifts and Pink Belly Swifts can be kept in that size as well, but are pretty high-strung.
Anyways, I replied to your thread... I wouldn't say the situation is hopeless at all. I think you have a good chance of finding your little guy, please don't give up on him, he depends on you