That assumes that the problem is with the supplier. When my brother worked for Threshers, a major problem was “the warehouse” determining what they should have, overriding local knowledge.
Assuming that the warehouse had loads of stock sitting around, of course. Often the issue is a supplier shortage or not ordering enough in the first place, and then the logistics people end up having to short store orders, and then get the blame for it. Gap on the shelf? Blame the big truck that didn't bring enough
When I was at Coop, the average on shelf availability in stores was about 97.5%, but the logistics function shipped just over 99.9% of the store demand they received.
Why the gap? Principally:
1 - poor forecasting from head office supply chain meaning either (i) not enough stock ordered from the supplier and/or (ii) the supplier not being able to react to a spike in ordering that wasn't forecasted
2 - supplier failure
3 - store stock file inaccuracy (the system shows positive stock that isn't really there, so the head office system sees no need to order anything) - poor store processes, markdowns/shrinkage not done properly, theft etc
4 - stock is in the store but not on the shelf
5 - poor system setup by head office supply chain - eg reorder trigger point set too low
Then you're into the less impactful stuff like:
6 - QC rejection / product recall
7 - significant warehouse downtime, eg systems/power outage, fire alarm, ammonia alarm
8 - supplier short term range reduction to cope with some crisis on their part
9 - outbound transport issue
10 - panic buying (eg Covid)
(And the problem for convenience retailers like Coop is that almost every line of a store order is for one case of the product, so not having enough inevitably means a store getting zero. For the big box retailers with more fast moving products a shortage might mean 5 instead of 6 and the customer impact is less obvious)