Sandy, You are probably guessing correctly, sad to say. It is not uncommon for the wax ring that forms the seal between the toilet bowl and the flange on the floor to spring a leak. One way that this can be caused ( I learned myself the hard way ) is thorough overly zealous plunging. If you have some floor covering, say sheet vinyl, the water could flow between that and the subfloor and leak through in a nearby room. The good news is that wax rings are inexpensive. Its a messy job, but not a costly one. Oh well, it will give you something to do in your spare time this weekend.