Welcome to the unpredictable world of turkey hunting. I had the exact thing happen to me on opening day this year. I was setup on a woods opening with a 2 or 3 inch deep stream about 30 yards from me. Even though the stream was only 8 feet wide that darn bird wouldnt cross it.
I would have been sitting on the other side but the area across the creek was a small game only area. Always, always make sure there is no obstacles between you and the bird. Sometimes they'll cross, but most times they wont. Especially the older stubborn ones. Better luck next time.