disappering colon polyp?

I've had 3 colonoscopies due to a history of polyps and also family history of colon cancer.  
My first 2 procedures 3 yrs apart were painless and polyps were removed (they were not cancerous.)
My medical notes state that at my 2nd procedure there were 3 polyps but one could not be retrieved.
The last colonoscopy I had was excruciatingly painful AND the dr. said it was normal.
What happened to the polyp that couldn't be removed 3 years ago?
Now I have to wait another 5 years, don't get me wrong, not anxious to have another (except he sd next w/be under general anesthesia, but am wondering  (I had to sign a waiver of possible missed polyps, cancer, etc.) DO POLYPS disappear?