Well... Sad news. I gave up the search/emergency measures last night. I probably could have called it off sooner but I figured what could it hurt? Well poor guy is gone. No indications the dogs ate him if they somehow managed to get access, or he got access, to each other. I was worried about moving 5 into a 10 gal tank for a bit, but it looks like that won't be a problem after all.

Thanks for the help guys! Too bad I didn't recover him. He seemed like the most adventurous of them all, so I guess he got his final adventure

Mods can close this if they want, thanks again guys! I'll be posting a regular hello at this point.