A mucocele is a small blister that forms as fluid builds up under the uppermost layer of cells in the tissue lining the mouth. It is only a cloged minor duct. There are tens of thousands of them lining the squamous cells of the mouth (and other areas of the body where the tissue stays moist) and they are there to keep things moist/lubiricated. They routinely appear clear. Untill unclogged they will reappear in the same logcation. They are nothing to worry about. You can't diagnose things from the web or comments from people like us who are not doctors, and have never seen the person in real life. Perhpas Dr. Wilke is a really good exception to the rule, However, I think even he would agree that not having actually seen the condition in real life, even his advice must be taken as a path of exploration rather than one of certainty. So while this is likely what it is, the motto around here is "When in doubt...check it out."