Found milky white substance under car

I noticed some milky white substance under the front passenger side of the car. I cannot say exactly from where because I noticed it after my daughter left for the store. The substance was odorless and maybe soapy feeling but it did not feel oily. Have not seen it before or since.
Checked the oil, under cap and dipstick- everything was normal. Coolant level is where it should be. Car does appear to run as it should.
I checked under the car but did not see anything unusual.

I read that there can be gasket issues, and other problems.

With this issue not repeating itself should I take it in to get checked out or wait to see if it happens again?
Anyone have any ideas what it could be?

 

Thank you for the reply.

2016 Prius.

It still has not done it again.