Only worked on one roof today.  The wind had blown a tab or two up but they were still attached. Over  time the glue strips don’t hold any more due to age, the cold, dirt blowing under them and the wind flaps them and sometimes takes them off. If your roof is hit by the wind and some of your shingle tabs hit the ground, pick them up and save them to be re-glued back on. This can be done with caulking or better yet with roof cement. Why save the old tabs?  Because its not the whole shingle, just the tabs,one or more, and trying to match your old shingles with new will be difficult as to size and color. This wouldn’t be a problem if you were going to re-shingle but that wouldn’t make sense when just a few tabs are folded up or off. New nails should be added too where needed.