By saving up research points until you have enough to buy the most expensive thing, you can unlock something, then just retry the level and you'll get your research points back.
I find it rather annoying that the trinkets that I spent a long time aquiring are no longer usable to me. Especially since it means I can no longer enter apocalypse mode for another 60 ranks.
Great game, but I wish there was some way to cancel recruitment. Twice it happened that I had just started searching for new units in another area when a unique unit popped up and there was nothing I could do to get it.