I was going through my mares and noticed that she didn't have a breeding history. She isn't Frame or White and I know that I bred her but it was most likely with a freshman so I can't remember who exactly.

Was she in a pasture with a stud?

As Columet is suggesting, she was pasturebred and you didn't have space so the foal "got away".

No I bred her with a freshman and then moved her to that pasture

Do you have the foal? If you do not then it probably was lethal white, died, and lethal white foals do not show up on breeding history.

Coldwater Ridge Farm said:
Do you have the foal? If you do not then it probably was lethal white, died, and lethal white foals do not show up on breeding history.

No. The foal wouldn't have been LW either since she does not have any LW patterns/color. I bred her with a freshman I was testing but I'm not sure which one it was as I had about a dozen to test.

Even if you search up the foal using her dam number, nothing comes up. So the foal 'doesn't exist' in a sense.