Only one way to find out.
Seriously though, I wash my carboys and buckets with lots and lots of water, over and over, and I've never had a thermometer sticker come off.
Even in the end, if it does come off, I'd rather replace a $3 sticker than a 5 gal batch of beer that tastes like hell because it fermented too hot.
We need rest. The spirit is willing, but the flesh is spongy and bruised.