mucus plug came out but not dilated?

So I went to get baby monitored and Doctor checked me and said she doesn't see my mucus plug, which I was pretty confused because I didn't see it come out (then again my toilet water is blue) so I'm just curious like when the mucus plug comes out when should labor start? Because I deff don't feel anything! Btw I'm 37 weeks pregnant with my second child 💙