hi I really think it is important that you get professional advice on this as it is such an important subject. It must be worrying you but only a specialist will know what is causing this and ways to prevent it. They will also have your medical details from scans etc. at hand to refer to. I hope they can help to provide advice on how to prevent this in future.
I had one. Was here one moment, gone the next. Woke up in a hospital bed 4 hours later. Brain scan indicated no damage and no reason found for it. Neurologist said a small clot created by surgery I had to take a skin cancer off my face, probably caused a tiny blood clot which entered my brain, caused the TIA and because I took 325mgs of aspirin everyay of my life, the clot dissolved and I regained consciousness. Damned scary!