From
https://livesofthefirstworldwar.org/community/702 - so it would seem that some survivors were picked up by Germans and made POWs.
"There were 20 survivors on HMS Queen Mary when it was sunk on 31st May 1916. HMS Petard picked up PO Ernest Francis, according to his report. One despatch stated that "Eighteen of her officers and men were subsequently picked up by "Laurel". A signal stated "It is understood that four Midshipmen and 13 men were picked up by Laurel".
Midshipman Dearden and AB Sherwood were picked up by the Germans and became prisoners of war. Midshipman Durrant died of wounds on 6th June. It is unclear whether Stoker Edwards was picked up by "Laurel' or by a Geman U-Boat [see his story]. Records would indicate that there were only 2 POWs. AB Brend (invalided 5.3.24), Stoker 1c Bower (invalided 7.2.17 fracture Rt Tibia & Fibula), AB Cunnah (slightly wounded left RN 11.6.27 time expired), Midshipman Dearden (PoW), Midshipman Durrant (died of wounds 6/6/16), Stoker Edwards (details unclear), PO Forster (pensioned 1.12.22), PO Frances (invalided Haslar 27/2/19), Acting Leading Stoker Hughes (Left RN 2.9.24), Ordinary Seaman Hutchinson (deserted 6.10.19), Midshipman Lhoyd-Owen ( ), Leading Stoker Manners (pensioned 21.11.26), Boy 1c May (invalided 18.3.17 severely wounded), AB Meads (invalided 27.1.22), Leading Stoker Ralph (invalided 11.8.19), AB Sherwood (PoW), Stoker 1c Smith (invalided Haslar 9.7.24), Midshipman Storey (placed on retired list as Captain 8.1.49), Stoker Petty Officer Taylor (pensioned 19.7.22), Midshipman Van Der Byl (invalided 15.1.19 disease of eyes)"