The tag agency took the title? Never heard of that.
I have a car that is currently black tagged, and has been for the last 2.5 years. I still have the title, and could sell it just like any other vehicle titled in my name. Or, I could insure the car, and take the insurance form to the tag office along with $5, and upgrade it to a regular tag.

Was this truck registered to you, in Oklahoma, prior to black tagging it? If so, I think you got ahold of a poorly trained tag agency employee......