from dictionary.com:
vin·tage /ˈvɪntɪdʒ/ Show Spelled [vin-tij] Show IPA noun, adjective, verb, -taged, -tag·ing.
noun
1. the wine from a particular harvest or crop.
2. the annual produce of the grape harvest, especially with reference to the wine obtained.
3. an exceptionally fine wine from the crop of a good year.
4. the time of gathering grapes, or of winemaking.
5. the act or process of producing wine; winemaking.
6. the class of a dated object with reference to era of production or use: a hat of last year's vintage.
adjective
7. of or pertaining to wines or winemaking.
8. being of a specified vintage: Vintage wines are usually more expensive than nonvintage wines.
9. representing the high quality of a past time: vintage cars; vintage movies.
10. old-fashioned or obsolete: vintage jokes.
11. being the best of its kind: They praised the play as vintage O'Neill.
As someone else said, vintage basically applies to wine making. But usage changes over time. So #6, #9 and #10 in the definition seem to apply to older fabric. I think you could also say 'vintage' applies to anything no longer in production or manufactured or created a long time ago.
Basically, most words mean what most people "think" they mean in their own world of knowledge. So some equate vintage with 'antique'(however that applies to fabric I don't know). I wouldn't take it personally. You certainly were only trying to give an accurate description as you saw it.
Nice fabrics by the way.