Lost Frost plugs

Well the big came to start the engine...when we added the water, it started to pour out over the floor. With a quick inspection, we seem to have lost 2 frost plugs when it was stored outside last winter.

We checked with the company that did a mechanical break in and they don't all water. Very odd.

Went to UAP to buy more and I gather they come in unique sizes so we will have to measure,

I *really* don't want to pull the engine (again) but I understand that the frost plugs can be installed with the engine in place.

Any tips and tricks ?

Thanks