If a person were to lose their memory, they would not remember anything, not even who they loved. I don't think the person would be falling in love with someone of the opposite sex if they've been gay or vice versa because their feelings and attraction didn't change. it's not a part of their memory.
Hold on, you're now answering a question you'd previously implied was coming from someone who might be mistaken for a closed minded idiot.
Perhaps you should first publicly acknowledge the change of perception that now gives enough validity to the question that not only is it not just automatically dismissed out of hand, but you are actually revisiting it to make another reply.
Me personally, I don't think sexual orientation would change, ..............!but I would just be guessing!
No other reply seems to provide more than informed guesses/opinions, so in fact the OP's question has proven to be one of the better more thought provoking ones Tim that you too can only answer with an assumption that may well be accurate, but for which you can offer no substantiation.