how do i run a trigger after a record is detached?
Detaching record from UI runs "After Update" triggers on both sides of relationship.
I did some testing to verify that triggers run as expected. Unfortunately I cannot go into details of your implementation. Try use Triggers debugger, this may help.
the trigger runs on all updates except detach. This is the trigger debugger results after detaching a record. Running update in stock stored on Sales Order Item: 3437A (ID=51601956)
update in stock stored has NOT ran
What is the type of your trigger?
Update Field Value
Formula returned NULL - in this case trigger does not run.