BA's last Concorde flight was in 2003. T5 opened in 2008.
I don't think the T5 designers had any brief to expect a Concorde.
And.............Concorde departed from the Concorde Lounge in T4. It was a very nice lounge. No-one paying for Concorde would accept anything other than a very special Lounge. A15/16 and 17 are just parts of the general Dump that is T5. (Other than the T5B lounge, of course).