L.W.
I went through the same thing when my son was 5-6 mos. old. He couldn't find it/get it back in on his own...so it was up to Daddy and me and it happened several times a night. I asked the doctor and he said "break the habit now...it will be easier than when he gets older!" He was right. It was only a couple nights and he cried at first for a short while, but was so tired...he would fall back to sleep quickly. I see now that my doctor was right. The older kids (and adults!) get...the harder it is to break a habit.
Good luck