Am I misremembering the shopping cart system with regard to sales and price change?

[A]

I do not often buy at the last minute of a sale. However, I was still on the fence with buying a game earlier.

I thought if you add a game that has a sale ending soon to your cart, you get to keep the discount for a few days until you're ready to buy it. Is this not the case anymore? I thought this was changed to what I remember relatively recently.

[miamew3]

I don't remember this ever being a thing.

[Pscht]

It never was "a few days". Minutes, maybe a couple of hours at best. NEVER days.

Next time make up your mind in the WEEKS a sale usually is going on. Or try isthereanydeal.com for legitimate key sellers.

[MancSoulja]

You're misremembering. If you make a purchase and that purchase fails, you get two days to repurchase the game at the price it was when it failed even if the sale is over.

[Dr.Shadowds 🐉]

I might be wrong, but this was for Steam events like Winter sale, summer, or etc. Anyways you add items to cart, and don't clear, or add/remove items. If this ever update, and unable to provide deal, your only hope is trying cart history, deal last only for few days.
https://help.steampowered.com/en/accountdata/ShoppingCartHistory

If it happen not to have history cart there then there nothing can do about it.
-edit-
This seem to only apply when fail purchase.

[cSg|mc-Hotsauce]

It only applies to failed purchases and the cart will be saved for 72 hours...

https://help.steampowered.com/en/faqs/view/26CE-6A3B-C548-5AB4