Any idea what would make one lose it's magnatism?? I went to clean up the stove top last night and found that at some point the thermometer has stopped being magnetic! It's not like we took it off the stove or anything over the summer...I'm baffled. Is that going to effect the temp readings? I can't see how, but...I also can't see how it suddenly demagnatized itself sitting untouched on the stove top.