How likely it is that when fat is reabsorbed it will remain asymmetrical & need a touch-up?

Grafting fat successfully require a number of variables to all be lined up correctly. Fat has to be gently harvested in small individual intact particles then diffusely grafted through vascular soft tissue without placing excessive amount of grafted fat in any one place. You can think of it as a chessboard. White square a grafted fat and black squares are live vascular tissue. Every white square has to be surrounded by black square in order for the process to work.
Grafting fat works best by adding small diffuse volumes of fat over large areas.
It’s kind of the opposite of having your buccal fat pad removed.
The buccal that pad is one solid collection of fat and when it removed there is virtually no host tissue to support grafted fat in that small area.
A bit like a lot of black squares have been removed from one area in the chess board. That makes having each white square surrounded by black squares not possible.
It’s going to be very difficult to get enough fat to survive in such a small area to compensate for buccal fat pad removal.
The Procedure you had is permanent and irreversible.
It’s not possible to reverse the effects by grafting fat.
On top of it is the buccal fat pad is deep in the cheek not superficial or close to the skin where we typically graft fat.
Filler on the other hand can give a substantial volume in small spaces and that is the treatment of a choice for what you describe.
Without pictures we can’t make an assessment but its unlikely grafting fat can restore your face to pre-bichectomy at least not with one procedure.
Fillers are probably going to be far more effective. Attempt at doing this with grafting fat will probably require multiple treatment grafting conservative amounts of fat six months apart and even then it may not look similar to before your procedure.
I continue to warn against buccal fat pad removal because it tends to create problems with premature facial aging down the road.
In making an accurate facial assessment most issues (especially in young people) tend to be based on skeletal structure and not soft tissues. This is why soft tissue manipulation often doesn’t give the results people had expected. The reason is that it isn’t treating the primary problem which is usually based on bone structure.
Grafting fat in the face is unpredictable, imprecise and unforgiving in comparison to fillers.
Best,
Mats Hagstrom MD

I have been warning people for ye ars against doing buccal fat removal (Bichectomy) because the face inherently loses volume with age and, even if you look OK immediately afterwards, your face will look gaunt in a few years. Also, it is almost impossible to replace it since the buccal fat pad is well circumscribed and globular. Thought you can replace fat in the area with fat grafting, it is very hard to replace that which was removed exactly. Make sure you see an expert in fat grafting who also knows the anatomy of the area exceptionally well.