It is in German, describes D. claudiea, yet shows images of the same frog I have pictured above. I was of the understanding that claudiea looked more like lugubris as indicated by the bdg "guide" here:
If you have access, read in Jay Savage's book Reptiles and Amphibians of Costa Rica, that's where I'm pulling my description from. I'm also just going by experience seeing them in the wild. I always confuse C. flotator and C. talamancae, so I'm not the best-- hence why I looked it up.
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.