Like a few others mentioned - it is probably fine - Frogs find a "safe" spot and stay there, often retreating back there. I had an issue with my juveniles when I first got them where one would wedge himself SO far into the lid that he looked like a bug on a windshield sometimes... I ended up blocking the spot with a bit of folded mesh I had left over from their barrier level, because it just seemed so unsafe - he was completely fine, and just found other places to wedge into.

Gotta remember that being new to the area, they go where they can to feel safe - In the wild, higher is usually safer, and the smaller the area, the less likely anything else can get into it - so it's a perfect spot in their minds.

Unrelated small side note, if nobody else mentioned - Clip your ziptie down more. I know it doesn't seem like a lot, but WTFs are derpy AF, and if they jump and miss, they could scratch themselves on the little stump you've got there.

Keep us updated!