Either the OP's inventory was full, or the OP wasn't LtCm yet.
A lot of the writeups of the ships on the Tribble C-store are wrong, indicating the ships as one tier lower than they should be (from Cryptic's old internal numbering system, with the Miranda being T0). Therefore, the LtCm c-store ships are mistakenly called T1, the Cm ships T2 (etc.).
This has been mentioned more than a few times and hopefully the writeups will be updated before the system hits Holodeck or there will be a *lot* of confusion when people try to buy ships.