Yep, we too have been having frogger problems... I keep transplanting the little buggar back to the trellis or other locations.. only to find him on the edge under the cover flap, or on the top lip, or the last time we found him (or another one, who knows) enjoying the soak at the waterline.
Our little frogs are about a inch long; here's a specimen on our mint plants:
Put the lime in the hottub you say? Or on the outer edge. We'll give it a try!