I brought my one year old to daycare and this horrible thing happened!!!?

Hello. I have a gorgeous, healthy chubby happy one year old baby. Now I brought her to a daycare thats right inside my gym. I packed her a bottle with cereal in it. *choking hazard for her not because its a thicker smooth consistancy* also packed her some cheese in small cubes and some banana cut into small cubes, and a baby food chicken dinner to eat. Anyways I get home and a friend phoned me and said an employee at the daycare contacted this girl named Shannon and told her I gave my daughter sour milk, and asked the question that if my daughter isn't walking by age one year and a half do I lock her in her room and leave her there by herself until she walks. WHAT BULL! I would never ask such a lunatic question as that. It really angers me this unknown daycare worker would lie and say these crazy things! Every check-up at the doctor has been an A plus for health and weight. I know that this is an unknown daycare worker because she described to a person my friend knows what my daughters bottle looked like that mourning in daycare. I called the operations manager of the daycare, and she told me that she has a zero tolerance for her workers going outside of the workplace and spreading rumours. But we don't know who it was! WHY WOULD THIS WOMAN LIE and say I asked a lunatic question when I never did, and the sour milk. This just makes me so mad. Do you think I could have a case for slander? I am an excellent mother,clean and I love my daughter. Anybody else have any input or ideas to tell me please. This kind of rumour can get me into trouble for no reason!!!!