Any more suggestions on how I can find my lost cat (I'm hearbroken!)?

I've done all the obvious things of couse like callen animal control, the local Humane Societys, checked with neighbors, put an ad in local papers, and put fliers up at any stores that will let me. We live in a semi-rural area right by Lake Michigan. Most of the neighbors are wealthy and have weeekend and/or summer homes and I haven't been able to speak with them yet it being off-season. The problem is that she managed to get her collar off with her tags (which I found)! I'm thinking that since she is friendly, adorable (all white!), housebroken, and spayed that someone just umed she was abandonded sicne she was missing her tags! I wish people wouldn't do that if the cat looks healthy! Just leave it be and it will wander back to its home. My 3 cats are indoor/outdoors and are all fixed and VERY HEALTHY! Since our road is 3 MPH and there is little or no traffic, not one is ever gotten hit and that's in the 35 years of owning 17 cats at this home. They live the life here, it's paradise! Even in the cool winters, they can come inside anytime and curl up by the fireplace! I was going to have them all micro-chipped and now I'm kicking myself (although if someone wanted a cat, that's not going to stop them, would it???) for not doing it. SO what else can I do? I was on vacation when this happened and my mother was feeding them (we share a home) but she doesn't pet them (she's a dog person, lol!) and she probably missed me and went looking for me! Please no lectures about how cats should only be indoors if you live in an area with loose dogs, wild animals that could kill them, they are very old and getting senile, lots of traffic, rampant diseases that vaccines won't helpt then yes, they are better off inside only. Thanks if you are kind and helpful. That is rare on this site where you tend to only get lectured which is a shame!