Running on the latest version (5.0.176), treasure enchantments will appear available at night, when you add it to your tool it will appear to use up your exp and add it to the tool properly, but will immediately remove the enchant when you take it out of the slot and relogging will give you back your exp, so no real harm here but it is quite annoying.

This happens to me almost in every try to apply the enchant to some tool on mc 1.12.2