Your solution worked! All I did was place the parameter "&merge_base_part:fid_1" in the drawing note, and it automatically updated to "&MERGE_BASE_PART:FID_1:4" giving the p/n of the base part before the mirror.
Who would have known this parameter already existed in the part model and could be used in a note of a mirrored part drawing? I did not see any reference to it in PTC's technical support knowledge base, and would not have know it existed as the PTC tech. support engineer suggested I try a another technique that did not work.
In Reply to Matthias Stueber:
This should work:
Create annotation feature with "&merge_base_part:fid_1" --> Feature Parameter updates when mirror ref part is renamed.