I don't think you're being paranoid after all of the stories of the losses out of pax bags, but I think it depends on the airport and what you plan to pack.

I don't have time to do a full search but there's something that's telling me that when loss stats are put out there LGA ranks above most airports (loss of contents from inside your luggage, not loss of the luggage itself). Don't take my word, though - a quick search should turn up some info.

I have had many, many long layovers with no problem at all at some of the largest and busiest airports in the world, but the one time I was dumb enough to forget that I had cash in my bag - at a much smaller airport - it was missing. There's never a guarantee.

It really comes down to how comfortable you are with the airport and what you've packed. Don't give them a reason to go into your bag and they probably won't. Personally, I'd pack accordingly, make sure I had everything valuable and/or necessary in my carry-on and leave my bags at the airport.