I pulled up a list of products that contain acetylsalicylic acid and Mucinex is not listed in the oral medications list. As for the topical medications, Vicks is not listed, but these are:
Analgesic Balm
Arthrocare Lotion
Banalg
Ben Gay
Compound W
Deep-Down Pain Relief
Freezone
Icy Hot
Mediplast
Mentholatum Deep Heat
Whitfield’s Ointment
Could your g-pa have been using a Vick's LIKE ointment, like Mentholatum? They are similar and he may have used the name Vick's like a person says "Qtip" when really they just mean a "cotton swab" or something...
Or g-pa may be taking more aspirin than he thinks he has. You said he has alzheimer's, correct? Is someone helping him with his dosages and meds to monitor exactly what he is consuming? If not, sounds like it would be a good idea...