What does it mean when a man and a woman's eyes suddenly meet?

Unfortunately, it happened at work. A new hire was in the hallway outside of the manager's office. I was attending a meeting and when it ended I opened the door forcefully and wide, so others could follow behind me and when I did, our eyes locked onto each others. At first I thought he was an ex-husband from 20 yrs ago and I think that's why I lingered a second but realized it wasn't him and moved on. Now he keeps watching me throughout the day and I keep ignoring it as best I can, however he keeps creeping into my thoughts when I'm at home. Yes I'm single, over 50, and very lonely but I have ruled out romance because I'm constantly choosing the wrong type of man. And I definitely don't want a work relationship because everyone is in your business. I figure this guy is probably not even single, (in which case, he'd, again be the wrong type of man). We are not allowed to wear jewelry at work since it is a factory therefore no wedding rings. I once made coincidental eye contact this way years ago on the job but I dismissed it because I was married.(Although it turned out I should have explored it with him because my husband was cheating on me at the time but I didn't know it.) What can I do to stop him from creeping into my thoughts before this goes any further? Does it mean something when this happens between a man and a woman? I know I sound naive but it's because most likely I am when it comes to flirting and romance. Does anyone have any advice for me?