Am I being petty n just drop it?

HeI'm changing baby's diaper abt 20 mins ago and I noticed a difference in the diaper...I realised my mother in law fed my baby food behind my back..(MIL babysits during the day while I'm at work..she's paid). So I was like 'Hun, someone give baby food today'. He was like 'how u know?' I told him I know. He said she had a lil piece of breadfruit. I asked him how does he know... He said he give baby the food. But we both reached home from work abt an hr ago. N baby had food during the day cause she already messed the diaper. I am upset that I didn't know n my sig. Other told me I'm being petty.