Why did my forces disappear while they were heading to a Stash?

Sometimes, forces heading to a Stash will be interrupted and will instantly return to your Catacombs. This can happen in the following situations:

• The Stash disappears while your forces are heading towards it. This can happen if the Stash has been vacant for 24 hours.
• The player controlling the Stash withdraws their forces while you are attempting to Scout the Stash.
• The player controlling the Stash withdraws their forces while you are attacking the Stash.