Yeah, It was an iPhone, you can tell from how they try to read it, NFC is set up for apple pay, so along the “TOP” edge
Check out this Wiki, It may help your repertoire when you realize not all phones and NFC antenna placements are the same, Another reason you may want to consider a Flex in the future 
One other issue you may come across is Phone covers, they can somewhat diminish the readability, so bear that in mind