My mom has been gone for a long time?

Okay so me and my dad have been home together. They are both married and she hasn't been depressed lately or anything. Earlier today like @12 or 1pm she said she had to go run errands. So now its 10:37pm and its been hours and she hasn't come home. Same thing happened yesterday and she got home around 3am. Its really annoying and it makes me sad because me dad is downstairs and sleeps alone now because shes never at home. Idk if shes cheating or really doing errands? Idk it just irritates me