Now that you mention it the dock did have a lot of garage.. Memorial Day weekend lots of ppl throwing things.. Could very well be a plastic bag.. Ganna pull the impeller and thermostat just for piece of mind.. But lot of different things that could have happened.. More of a mystery now..

If you pull the impeller, you might as well install a new one. No reason to reuse it even if it "looks good". Cheap insurance

The impeller is brand spanking new maybe been out 3 times on it.. Lol but your right ...I wanna check it just In case it had a catastrophic cluster fudge...lol