Sorry to revive an old thread, but I imagine others may search this topic as well (as I know I did!).
I found this to be successful for me, after some trial and error with various methods:
Clear tubing used for air powered fish sponge filters, cut to various lengths (depending on where in a tank I need to access, ie. I did one short, one medium and one longer).
Pack the end with Sphagnum.
Leave the tubes in the tank for a week+.
I've caught 8 little guys this way, but not necessarily how you might think, let alone how I thought!
About 5 of them I caught by placing fruit flies into the tubing after it had been in for a week, then placing it back in the tank. After about 10 minutes, I returned and found various frogs inside the tubes eating away. Plug an end, remove!
The remainder, I found were less spooked by the tubes after they had been in there for a bit, so were a bit less jumpy when I took a tube during feeding and caught them by slowly placing over their bodies on an angle, and shooing them in with some tweezers (similar to the glass tube method).
This is for R. imitators. When I started trying to move the offspring, I was quite disheartened. Now, I have been able to move every frog I wanted within a 2 week span.
I should mention as well...patience is key.
Hope this may help someone.
Regards,