Thanks for the quick response & advise, I updated my location info and added a signature, with some of the pool info. I use a solid winter cover, but not a safety cover. It is just held in place by water bags. It's possible that it could have been runoff from the yard as we did get 2-3 inches here last week. My concern at first was that when I took out the gizmo in the skimmer the water level didn't drop in the skimmer, my thought being it filled up from the bottom rather than the top. however it did drop once I opened the lines at the pump.
The cover was pumped off and dry when I removed, and we rolled it to the opposite side of the skimmer so that wouldn't have been the culprit. So it my be much ado about nothing, hopefully is, but it still worries me a bit that my pool level dropped a around 6"-8" over the winter. If I recall correctly last year when I opened it it was actually a couple inches higher than closing. This is only my second year with the pool so I'm still a newbie in most senses.