In our on-site, fully-accredited office surgical facility, where my partner and I perform all of our cosmetic surgeries, we have the following policy regarding touch-up or revisional surgery--which your situation certainly is: There is no surgeon's fee, but the patient is responsible for minimal operating room, anesthesia, and, if necessary, implant costs--none used for tummy tuck.
"Free" touch ups might become problematic, as some patients always want 'a little tighter," "a little higher," or "a little smoother." With "free" surgery you could see chasing an abdominal dog ear scar all the way around to a butt lift! So sharing the cost of revisional surgery seems to keep both surgeon and patient on their best behavior! And, it keeps the surgical costs to a reasonable price in the first place, since those doctors who offer so-called "free touch-ups" are actually "including" these costs in every operation! (Do you get a refund if touch-ups aren't necessary?)
Obviously, if you've spent a tidy sum for extensive surgery, we want you to be happy, and I'd rather not tie up myself and my staff and my operating room time with "free" surgery (since the rest are actual overhead costs, and I only take home the professional fee), so I really do my best to make my operation the best I know how. That keeps do-overs to a minimum, and yields the maximum number of really happy patients!
Check with your surgeon; this should have been spelled out prior to your tummy tuck, but even if it wasn't, or was somehow forgotten, he or she does have a policy to deal with these situations.