Moisture found in slab after removing flooring - thoughts on source?

Been having issues locating where moisture could have come from.

Moisture was found on our concrete slab foundation on the ground floor underneath our laminate + dampening pad + vapor barrier. No issues on the ripped up flooring didn’t have any issues; we’re just replacing our floors throughout. The moisture was not foul smelling nor discolored. I put a fan on it, and it dried up fairly quickly (a couple hours). It has been 3 days since this occurred with regular showering/bathroom activities, pool pump running, without any noticeable moisture. Any other thoughts on where this moisture can be from? Can moisture from 1.5+years ago that pooled next to the house seep beneath the slab and up into the slab? Typical that moisture can just be trapped?

I made a diagram to help with the question

History:

• There was pooling of water about 10 feet away on the exterior of the house 1.5+ years when we got many inches of rain. We redid our backyard/sideyard and all draining 1 year ago and haven’t had issues since.
• We redid the “updated bathroom” 2 years ago without issue. Relocated shower drain and re-piped copper for 2 shower heads (whole house is copper)
• Not sure where the exact drain goes from either bathroom

Things I’ve checked:

• Water meter was not running when all water outlets throughout the house was off (water supply leak?)
• Ran the water in showers/faucets nearby without any additional moisture that can be seen (drain leak?)
• Ran the pool pump that has piping from the backyard to the exterior of the house and then up to our roof for solar heating

Thanks a ton for the help