This is how the Life Cycle of a SKU can be defined in a Warehouse
i) - A SKU gets received for the first time - Typically items get downloaded into the Item master of the WMS even before they hit the Receiving dock.
ii) - The person at the receiving dock receives the SKU, and then the WMS flags the SKU as a new SKU, so it gets sent to an area called Cube measuring area, here the Volumetric dimensions, weight, picture if picture tracking is enabled) etc are captured
iii) - Then warehouse personnel assign a bin location or an each pick location or an active location for that SKU, typically it is a permanent assignment, so the SKU resides there as long as there are orders for the SKU
iv) - Then the SKU gets putawayed there - meaning it gets sent to the bin location first and is available for pickers to pick to fulfill against any orders - now this location can be looked up from the WMS, any basic WMS should have this feature - lookup SKU and quantity in bin locations by entering the SKU
iv) - Also the bin location has a min and a max, so depending on the SKU volume buyers might be buying more of that SKU, if there is no space for that SKU in the bin location, then that SKU gets sent to Reserve storage and stays there, until there is room for that SKU in the bin location. Again all WMSs have the ability to look up SKU in reserve storage, all the SKUs in reserve storage stay as cases, so it is matter of looking up all cases by SKU in reserve storage
v) Once the SKU runs out in the bin location, the SKU from the reserve storage gets replenished into the bin location.
vi) Obviously the last part is once the SKU doesn't receive any more orders, then the SKU gets purged out of the system, first the inventory gets to zero, the product gets moved to a deep reserve storage and eventually gets sold then the SKU is deleted from the item master - typically it is not deleted completely, rather the status is marked as deleted
So anybody should be able to look up a SKU from the bin location first and then from the Reserve storage, you can also look up the same SKU that is Outbound towards a customer, but that doesnt matter because they are already shipped to a customer, so they cannot be used to fulfill other orders.