The RAF museum Story Vault includes the next-of-kin and Casualty Record Cards for both AJ Mayo & JW Jones –
http://www.rafmuseumstoryvault.org.uk/
The latter is on the Arras Memorial, so I assume that the body/ grave was not identified after the war.
Ancestry has quite a lot, including RAeC Ticket & photo, probate record (he left £687), Army record of effects, listing as civil engineer, etc; but no Medal Index Card or Medal Roll entry.
I think, as an officer, his next-of-kin had to apply for his medals.
You used to be able contact the MOD Records Office at Droitwich (and claim previously unclaimed medals, or pay for replacements), but I see their website – https://www.gov.uk/apply-medal-or-veterans-badge – states that they no longer issue WW1 medals, presumably because the last veteran has died and all records have been handed to the TNA (PRO).
Still, I would try them first, explaining that the TNA cannot find any record, and see what they suggest.