Yes ask your surgeon the questions. I'm not too concerned about the graft - I could probably done without it but I guess there would have been functional difficulties with it if i hadn't had it.
It's very surprising the MRI didn't pick up your tumor - especially one that size - mine was 1.4 x 2.4 cm and was readily visible on both MRI & CT I would love to have someone else read it - the results might be different...

usually they can find it even if it's under the graft - either by CT or you will likely feel it - pain - and the graft could fail depending.
My problem was similar to yours - I'd had an ongoing issue for years.
My surgeon said the wrist graft tends to take better because sometimes he thigh tissue is too thick!
Anyway good luck - see your surgeon says! And take care!