It's pretty strange, but you have your back covered because all undelivered clicks will be refunded in your udimi wallet at least.
The seller has 100 hours in total to complete the delivery. However, in any case, if the seller fails to complete the delivery, the total value of not delivered clicks will be refunded to your Udimi balance. But I hope the seller will complete the delivery on time.
For further assistance, please contact Udimi support from the Help page.
The guy must already be signed up, or he would not be able to see the forum. So I am not sure if this tactic will work for you. Good luck