This is a good point. I have spoken to Gwyn the Town Clerk and to Ap Thomas the architects today.
It appears that the plaque is intact, the methods of insulation/rendering etc. have meant that it has not been damaged by the development.
The stone itself was structural to the building so not something easily removed. The development has meant that the original stone is now a piece of 'hidden history' ie. no longer visible in the structure.
There is the possibility that a new plaque will be installed referring to both Ashley Jones and the new development and that is currently with the Council.
David Price wrote
Until the current alterations, there was a small plaque to commemorate that the bus shelter (1930s) was given by W. Ashley Jones (who gave the fields at Siliwen). I wonder if the plaque has been incorporated into the rebuilt Hafan?