How can i find out who has done a background check on me

I was recently "encouraged" to take an early retirement. in this Company Virtually every retirement merits acknowlidgement and a party by the team one works with.
No explanation was offered. i had to clean out my office immediately under supervision. i was told that i had done nothing wrong and that there is not a "No rehire"0n my record.
I think my "release" resulted from someone doing a criminal background check and uncovered that i had been arrested and jailed for one day 4 years ago. my arresting officer lied , but to combat the report I would have to testify in an open court and I - certainly would be fired when my employer learned of it - so i pleaded guilty in the hope that the lower profile would help me to hide the event.
it would greatly ease my mind to know if that is what happened. if no-one did do a check i could seek employmen in my field - if it that did happen I would not expend any more energy and anxiety over that and explore my options.
another question.......is it correct that a criminal act can not be expunged until ten years after the event, but can be sealed at the judges discretion at any time?
your answer could change my entire life. I look forward to your reply.
Many thanks.