You'll have to train another one. The only way to do that is to fix and repair your huts. They don't like doing that so you will have to keep dropping a village on a hut until he becomes a trainee, and then he will help the others on the statue.

also if your builders have children they may possess some construction skills

I always leave clearing the leaves from the Roll to last. Then, when I need to train a villager, I'll set him/her to work on clearing the leaves. As soon as an armful of leaves is picked up the villager will gain some building skill. If the villager is interrupted before the leaves are put down no progress is recorded in clearing the leaves, though. That means that villagers won't wander off from other tasks and clear away the leaves before you are ready. By dropping the villager on the leaves then picking them up again as soon as they've gained some skill, they'll reach trainee level relatively fast, and can then go on to work on the statue or other tasks for the builders.