I own my condo, Elfmama. And I watched the lock technician (from a BBB member in excellent standing locksmith company) as he re-keyed the locks.
Once in a Staples store nearby I encountered a staff member who used to live in the complex where I do. She said that when she was there, some of the occupants (unfortunately, over 70% of both the tower and townhouse units are rented) had been accessing the residences beside them by going through the wall in the top-floor crawl spaces. After I heard that, I put a door security bar http://www.youtube.com/watch?v=luC_NnyMB1I
to secure the 4' high door to my crawl space. With 168 townhouses and another 480 tower apartment units, finding a culprit is a task even the police couldn't take on.
As far as keeping track of my meds, I keep the bottles in a metal lockbox which is then shut in a free-standing cabinet which secure with a large keyed lock when I go away overnight or longer. I keep track of my prescriptions by marking on the label how many are left in the bottle after I've poured the doses for the week ahead. That's how I realized that the pills in question were actually missing, rather than a matter of my having forgotten to pour that one medication. ( The Saturday in question, I had 16 in the bottle. I poured 7, changed the total on the label to 9. When I realized the "PM" slots in the dosette were all devoid of that medication, I checked the bottle - and there were 9 in the bottle.)
I am thinking that I may have the locksmith replace the deadbolt, rather than just re-keying it. Even if someone has managed to finagled a key for the knob lock, a new deadbolt should stop the incursions.
ETA more explanation