I bet it's talamancae. Last month I was in both Bocas and the Talamanca area of Costa Rica. In CR I got a shot of a C. talamancae (it had to be, that was the only species in my area I'm told), and it looks just like your mystery guy. The Colostethus I shot while in Bocas was slightly different-- I'm guessing flotator. I can send you the photos if you'd like, but they probably won't say anything you don't already know.