I am with a company that is unionized and have recently been put on disability. All employees receive their vacation pay on their anniversary date. I will be on disability when my anniv. Comes up next week. Will I still get my pay or will my employer hold my check until I return to work?

You need to call your Union rep. or shop Stewart. In some cases you have to use up your sick leave and vacation before you can go on disability, others only your sick leave.

The answer may vary depending on your Union and your contract.

Yes, this will be decided by your union contract or rules
So I agree to contact your union rep, My guess ( and that is all it is) would be that you would get it when you return to work