For me I wouldn't bother since so much time has passed between the last conversations and also since you only knew each other for a short amount of time less than a year and only met once. But if it gives you peace and stops the nagging question of "why..? what happened?" then text him if his number is the same as previously when you talked but if he does not reply do not send anything else his way. I had a much longer relationship that reached engagement and I still never got the full truth off him probably never will, some people men and woman want the easy way out, no questions ask they just go.
“If you worry about what might be, and wonder what might have been, you will ignore what is.”