I think my baby got bit at daycare

LO is 18 months and has been at daycare 2 so far. She's been bitten before and they filled out an incident report and had me sign it.

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I picked her up 3 hours ago and didn't notice this at the time-i pick her up on my lunch break so we hustle to leave, get home, and I clock back in for an hour.

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All her teachers said was that she had a really good day today.

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The bruise she has is on the inside of her wrist and is the right size for a toddler mouth though there are no teeth marks.

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I understand kids are going to bite each other and all that, my concern is just not getting told. I want to address it on Monday but I'm not sure if I should email the director or ask her in person at dropoff. I also can't rule out that she did it herself while I was in the bathroom or something but she doesn't have a history of that kind of thing-only reason I say that is because I didn't catch it right away.