A few weeks ago I was on my way home from Ada, OK to Sullivan. I called up Ft.Worth center for flight follow and got my Sqwk code. They handed me off to Tulsa approach. I have made this trip several times and this was the first time I was handed off to Tulsa. As I got closer to the MO, AR,OK boarders I was expecting to be handed off to Razorback like all the other times. I was nearing my time to descend and called up Tulsa to let them know I was starting down. They ask me my location and when I told them where I was, they told me I had been out of their radar coverage for sometime and to sqwk 1200, change frqs and have a good day. Has this ever happened to any of you? Are the controllers getting so busy the can't keep up? This was a first for me.