I assume you had a vitrectomy for complications of proliferative diabetic retinopathy such as; 1. vitreous hemorrhage, 2. retinal detachment
More often, vitrectomy is performed for non-clearing blood in the vitreous. During the operation, blood is removed from the eye which then clears the path for laser to be performed at the same time.
Pan-retinal laser (PRP, scatter) is the gold standard for proliferative diabetic retinopathy. It can be done in the office setting unless there is blood in the eye.
There are two scenarios after having had a vitrectomy;
1. Re-Bleed (everything was fine until recently)
2. Bleeding occurred during and immediately after the surgery and has yet to clear 3 months after vitrectomy
I"m guessing your situation was #1.
This probably mean that you might require additional PRP (laser) if the bleeding is due to the diabetic retinopathy.
This is not uncommon.
Make sure to stay in touch with your doctor.