OOC:
At this stage in the game, assuming a DC 15 as the baseline seems fairly reasonable, so a 14 is a failure. However, I try to allow "fail forward" moments outside of combat. This just means "yes you do what you want, but unlike a success this will cost you."
What kind of cost would you think is appropriate? Here are some suggestions, but you can propose one that is similar to these.
- Unbeknownst to you, the thing you find is something one of them was coming back for. They see you found it first and retreat, but now they know you know who they are and are coming.
- You find something, but it is cursed. A minor curse is given to you for touching it without being a member of their group.
- You find something, but only if you are willing to spend a lot longer than originally planned searching. As such, more of the enemy's plan will be finished when you arrive.