Truffle dough not sticky enough

Was the dough super crumbly even before you put it in the fridge? Or was it crumbly only after you took it out and tried to work with it?
If it was crumbly beforehand, I might try the recipe again and make sure the butter is fully creamed with a mixer (ie that most of the brown sugar granules are broken down) before slowly adding the flour.
If it's crumbly only after you've taken it out, it might not have mixed completely beforehand. I'd let it come back to room temperature and mix it -carefully, so you don't over agitate the gluten in the flour- and see if that helps.

It's so frustrating when these things happen, I know! Fingers crossed that helps a bit. And hoping maybe one of the better experienced bakers on here might be able to chime in as well.

The butter is just softened, not melted. And yes, it's incredibly crumbly. Here's the recipe:

1/3 cup butter, softened
1/3 cup packed brown sugar
1 tablespoon vanilla
1 cup all-purpose flour
1 cup miniature semisweet chocolate pieces
4 ounces dark chocolate or semisweet chocolate, chopped
4 ounces chocolate-flavor candy coating, chopped
1 tablespoon shortening
directions
1. Line a 15x10x1-inch baking pan with waxed paper; set aside. In a medium bowl beat butter, brown sugar, and vanilla with an electric mixer on medium speed until combined. Beat in flour just until combined. Stir in chocolate pieces. Shape dough into 1-inch balls. Place on prepared baking pan. Cover; freeze about 30 minutes or until firm.
2. Meanwhile, in a small saucepan heat chopped chocolate, candy coating, and shortening over low heat, stirring until until melted and smooth. Remove from heat.
3. Line a baking sheet with waxed paper. Using a fork, dip balls into chocolate mixture, allowing excess chocolate mixture to drip back into saucepan. Place dipped balls on the baking sheet. Let stand or chill about 30 minutes or until set. Lightly drizzle with the remaining melted chocolate mixture.

Do you mean that your dough is crumbly? I might try adding a little bit more melted butter in. The ratios of the cookie dough's dry ingredients vs wet might be off a bit. Do you have a copy of the recipe?