Seems like since u16, some items that were regularly in the store have gone missing.
Right after the update, Raid Bypass Timers were missing from the store but since it was a popular item people noticed immediately and it was brought back within a day or two.
However there are some less popular items that have gone missing from the store as well but since so very few people purchased them in the first place they have gone largely unnoticed. Items like Touring Tonics, which I tried to purchase because of the terrible physics engine change that caused me to get stuck in walls multiple times while running to open the last door in mansion or right before killing Rushmore after his air elemental throws me inside a wall.
A few other items such as gargantuan ingredients bags have also gone missing and I'm sure many less frequented items as well. (yes even with show all items checked)
Turbine, if you're trying to run a business with micro-transactions, you may want to make sure the store is actually stocking all of the items. You're losing money every day this isn't working so I would assume this is closer to the top of the priority list.
While I'm sure there are many saying there are much bigger problems to solve first, perhaps the person who is in charge of the store is on a different team than the ones working on in game bugs and won't take up valuable bug squashing time. (I'd rather not get stuck in walls but if it happens in a challenge at least let me buy a way to recover the 6 star run.)