Castaway Cay - My size t-shirt not available

[Unisphere]

This is likely an odd question, but we (family of 7) recently completed a wonderful 3/4-day Disney WDW/Cruise package.

The shop on Castaway Cay had great stuff... including a particular surf-styled t-shirt (adult size M or L) that I wanted, but they didn't have any (only S or XL). When I asked the cast member at the register, she replied "then those are the only sizes left".

Does any one know if there are any post-trip means of tracking stuff like this down?

Thanks!