Is there any contingency plan available for relic loaning?

I'm curious to get this question answered by someone who knows the official policies or has experienced such an event before.

Let's say there are two players:

Player A is about to finish his relic weapon and just needs the last remaining 30 Montiont Silverpieces for his Ranperre Goldpiece.

Player B has lots of Silverpieces available to them and has seen Player A (who they don't know) shouting for someone to help loan them the 30 currency pieces and is considering whether or not to not to help player A finish their trial.

(For those unaware, this could be completed smoothly and the loan repaid within a matter of minutes since completing the relic trial instantly rewards the player with an extra 30 100-pieces that were needed to generate the 10,000 currency piece.)

Let's say Player B decides to loan Player A his 30 silverpieces to finish the trial, and Player A decides to betray him and keep the extra currency for himself with no intention of repaying it. (Let's just say for the sake of argument that player A has no care for their server reputation for doing this).

My question is then, what could Player B do? Should he just remain punished for trusting someone by mistake? (Consider if both players knew and trusted each other, but the betrayal still happened) I've heard rumors that they can submit a GM call to get Player A to send the currency automatically but this hasn't been confirmed as far as I'm aware. Sometimes it's said that if both players write some sort of in-game agreement or contract, the GMs can then look back at the logs to help with this.

Have players in the past come up with a contingency plan for this event before? If so, I'd like to know just for curiosity sake how such an event can be avoided without cancelling the loan itself.

In the past, GMs have stepped in and reclaimed the items if you state your complete terms fully in tells and they agree to it. When a friend of mine had his loan stolen (the guy transferred servers immediately), it took them around a month to get his currency back.

These relic loans are a silly idea if you ask me. First of all, it's not worth the risk of being double crossed the way you mentioned. Secondly, after you get your relic, you still need 5 Umbral Marrows and 300 Plutons. It makes much more sense to keep farming until you get the 10,000 piece currency, complete the relic weapon, then sell the refunded currency to get Umbral Marrows and Plutons.