So my plan was to build up the oven and then cover it so if it rained it would stay dry but I forgot to cover it and it rained the next day. So, I only finished about 3/4 of the firebricks and then it got rained on for two days only after about 10 hours of drying. Am I screwed, what kind of damage did this do?
You should be okay -
The mortar is still wet… the firebricks that you soaked in water are still very wet… It’s very doubtful that the rain penetrated the mortar to a point of effecting the bond. Give it a couple of days to dry and LIGHTLY tug on a few of the firebrick. If they don’t pop right-off, you’re a-okay!