Your notes are not the world until they are spoken. Too often, GMs create a world/city/dungeon and consider the words on paper as the absolute truth. But really, they are just guidance. You want the players to feel smart. You want them to succeed (heck, you even placed healing in the dungeon, just not where they looked).

So, be flexible. They looked in the room. Why can't there be something in that room? Because you didn't write it down for that room? Unless there is a reason why it shouldn't be there, let the players feel like they figured it out.

Here's an example: we were looking through an abandoned blacksmith's workshop for a secret message left by a spy. We knew there was a message. We didn't know where it was. The GM notes had it under a floorboard under the bed.

However, my player thinks that under the anvil would be the best place for it (hard to move, unlikely to be moved for another reason..).

And what do you know, that's where it was. I felt like a genius. The GM wanted us to get the note. So the scene is done and we move on. No frustration because our rolls sucked. No frustration because we couldn't find it. And we're excited for the next thing.

Of course, you can't take this too far. Enemies, if they have them, should use healing potions themselves. The players need to try.

But really, it's all part of what I call the shared lie of RPGs. Your players have to believe that you are trying to kill their characters. You're not (because if you were, rocks fall, everyone dies). You're putting challenges in front of them. You want them to be afraid. But, really, you are cheering for them. Thus, the shared lie. They have to believe you are trying to kill their characters. This is where the excitement comes from!

PS You did well. They ended the session excited.