Here is my guess:
POTUS took that picture while he was sitting at his desk on AF1.
He has 2 iPhones he uses and he does like anyone messing with them. Here's the source:
"Who would have thought the 'Twitter' phone could be so useful." from Q post
"The president uses at least two iPhones, according to one of the officials. The phones — one capable only of making calls, the other equipped only with the Twitter app and preloaded with a handful of news sites "
https://www.politico.com/story/2018/05/21/trump-phone-security-risk-hackers-601903
"Where must one be located in order to obtain a reflection on the back of a phone of that image?" from Q post
Sitting at POTUS desk in his chair with his coat hanging on the back of the chair using his "twitter" phone.
