I locked out my Mother-In-Law (accidentally, really)

Last week, my mother-in-law came for a visit. And, NO, that's not a bad thing-I am very lucky to have a truly good mother-in-law. She wasn't so lucky last Thursday though. My mother-in-law watched the kids during the day while my husband and I went to work. It was good for her to get some quality time alone with the kids without mommy and daddy being around. I handed my mother-in-law what I thought were the keys to the apartment. I actually gave her two of the same gate keys. My mother-in-law took the kids for a leisurely stroll through the neighborhood not knowing that she would be locked out for several hours later. Oh, and she forgot to take her cell phone. On my way to a doctor appointment, I get a cell phone call from my father-in-law. He informs me that his wife is with the kids at a corner liquor mart awaiting my call to the pay phone. The pay phone wouldn't accept my calls. I finally receive a call from my mother-in-law. I told her the bedroom window might be unlocked and that I'd be home as soon as I could. Three hours later I come home. My kind downstairs-neighbor kept my mother-in-law and kids comfortable for the last hour of their ordeal. My mother-in-law said I'd never let her watch the kids again. Honestly, the kids never crossed my mind. All I thought about was, "I've locked my Mother-in-Law out of the house." My daughter-in-law reputation has just gone down the toilet.
TIP: Always check keys before you pass them out & keep a spare set hidden somewhere around your home. (Another error I made-I forgot to replace the spare set!)