I think there is zero chance of any additional compensation as you got a meal even though it wasn’t a special meal - mistakes do happen but you acknowledge the crew and purser apologised and tried to make it up to you

i think 10,000 avios is on the generous side- although ba have been cutting back on compensation they are starting to improve but I think in your case you should accept what’s been offered and not waste your time pursuing further

if it was me I would be certain if I ordered a special meal and if it did not come on the manifest I would have explained to the crew you had ordered it - I note you’ve said they acknowledge they made a mistake which is fine but you seemed fine with the regular meal so I would say the purser done well in this situation in terms of service recovery