I have a speyed bitch(2 1/2 yrs old Shiba Inu).She is showing signs of being in season

.My males are all over her(not usual),she is temperamental etc.I have spoken to the vets and he says its one of 2 things.....
1/ infection...but he doubts it as it is happening at about 6 monthly intervals...not constantly.
2/ she has some ovary left behind from her spey

which is producing hormones and causing a season
Now the vet says he can take blood tests to check hormone levels and then if it is no 2 then he will have to open her up to find the offending bit of ovary...which he says is not easy as it could be very tiny.
Has anyone else seen'heard of this ? To say the least I am not happy with the vet who did the spay...but then I have already changed vets due to other 'issues'.
So on top of the cost of a spey I could be looking at another operation.:rolleyes:
Archer