Agreed, so annoying when you know they're BSing you and they still say it to you with a straight face.
The person I asked when I was trying to buy some 69A21/CL/TS lamps from was initially confused and thought they were no longer available but when I gave them the part # they were able to have some ordered in for me.
As for the F96T12 ballasts, I think you can still
order new strips for them even. Anyway at least you directed him to eBay, I probably would have pulled up the eBay page in front of him and shown him few examples.
The loose ballasts might be a bit harder to find now, I think I still saw them at Home Depot around 10 years ago.