Can the state of Florida place a lein against property without the owner being aware that it was done?

Liens are, by definition, a matte of notice. However, the method of providing notice does not always result in the owner necesarily being aware that it has happened. For instance, if they sent letter that you mother never opened, she might not be aware of it. but ultimately the recording of a lien is a matter of public record, and everyone -- including you and your mother -- may be considered on "constructive notice" by virtue of the fact that you could know. All of this notwithstanding, your question seems to suggest that you do not know whether a lien exists or not. You can ask a local real estate lawyer to do a title search on your property to see if a lien exists, and it won't cost you an arm and a leg to do so. If one is there, then you may need to know whether the facts are such that the lien does not (or did not) attach to your mother's homestead. These con be complicated issues now that it has been titled to you, so definitely spend the money and see if you can get this resolved. It may cost you less than treating a cold....