A plug is generally about that size, you can lose it and not go into labour for a while for some people it can be weeks others only hours, when is your next appointment with the Dr/OB/MW?

Keep an eye on any ctx/BH's and if there is a regularity in them or increasing in intensity perhaps go get checked out.

I know the plug can regenerate, if you lose bits of it, but in one big hit I'm not sure.

Best to be closer to a hospital if there is a risk of Pre Term Labour/Delivery.

Goodluck and hope you ahve a few more weeks to go