Night swimmers

And I don't mean us, the owners of the pool. We purchased one of those Easy set pool for the first time this year because the kids loved the neighbor's so much last year. We swam yesterday. No issues. Pool was fine and when we were done we closed it all up etc. My neighbor calls today to ask what's up with my pool and did I even see it? No I say and what do you mean?

Apparently it's lost alot of water since we closed it up yesterday. So either we have a leak (she can't seem to find one or any water pooling around the pool to confirm a leak) or someone was getting in and out alot without the ladder, thus letting bunches of water out from the side. I'm leaning towards the latter. So now the back light will stay on and if or when I catch the little shit that's doing it there will be hell to pay.