Diaper-Free Accident

It has been more than 2 weeks since Alycia has been off diapers during her daytime nap and so far, she's been good and has not wet the mattress. Yesterday was the first accident. I normally wake her up 1 hour into her nap to bring her to the potty that's placed next to the mattress on the floor. However, yesterday I got a shock when I touched the mattress and it was soaked! And she had slept out of the plastic mat placed beneath her. The mattress was totally drenched with her pee and since the mattress has been soiled with pee and puke several times already, I threw the mattress away. Today, she has to sleep on my mil's Japanese Tatami mat and Sherilyn has to sleep on the baby-size mattress from the playpen. I better go and check Alycia and bring her to the potty now. I have no more spare mattresses!