Maybe twice in all my active using years did I find a pill I didn't realize I had. I was always very cognizant of how many I had and would, in fact, tend to count them obsessively.
And, I personally never did do the carpet thing, (due to the nature of the type of drug I used), but there was this one drawer where I would usually keep my pills, and when I would run out, I'd look for dust or crumbs in there, from where I had broken one in half or whatever. I'd wet my finger and run my finger over the (usually very meager) pill dust and crumbs to gather it all up and eat it. Usually I would get mainly lint.
I have witnessed crack/coke users scan the carpets and floors, and once my daughter found a sizable chunk of powder that her boyfriend had dropped on a bedspread.
A friend of mine once dropped a Vicodin in my car as she was counting out her pills after picking up a script one day. We looked through that car for three years, from time to time, and never did find it. Occasionally, when I was out, I would would still go look under the seats and in the nooks and crannies to try and find the fuckin thing.
Yeah, I guess I'm no stranger at all to the "carpet picking" type of obsession, in its many forms.