Either the story is confusing or the process in general.
It is pretty strange that you realize that you have no stock when you try to post goods issue.
Usually goods issue in SAP is done after the stock was picked and often even after the truck has already left the plant.
A new determination of the nearest next warehouse with stock is then certainly at a wrong timing.
The problem already starts earlier, if you created a sales order to be delivered from storage location A, then I wonder how this stock in that location could be consumed by something else. There must be a gap, you have to analyze how this stock was removed and why it was not filled up again.
Is there no dynamic availability check for unplanned goods issues? Is there no MRP to guarantee that the needed stock is available at the right time?
Working with negative stocks is already in general an indication for wrong processes.