How can I make sure my players’ decisions have consequences?

Last session, my players got into what was meant to be a fairly minor battle. The wizard misjudged the strength of the enemies and used both of his third level spell slots, and the druid acted sub-optimally, but in character, by using several of her healing spells to wake unconscious enemies for interrogation.

The idea was that after this battle they would enter the dungeon and work their way through to the boss encounter, so there would have been resource management consequences for those characters.

In fact, they ignored the dungeon entrance when they found it, and decided to carry on the way they were going and maybe come back and deal with it later if they felt like it. Yes, I know this is something I should have been more prepared for, but I thought I knew my players! (They usually like killing things and collecting treasure…) The town they were heading for was more than a day’s travel away, and I hadn’t intended there to be any more encounters along the route, so in the end I just said they carried on to the town, which meant they got a long rest ‘for free’ and didn’t have any consequences of their decisions. (I’m not trying to punish them, but I think it’s more interesting if they have to think about all these things and can’t just blow all their spells on one battle a day!)

How should I have dealt with this situation on the fly, or when prepping for future sessions? Some ideas I had afterwards:

  • Have the next set of enemies emerge from the dungeon and start a fight, thereby trying to force the players to do what I wanted them to. I feel like I don’t want to railroad them this much, and I already feel like I throw too many unavoidable fights at them.
  • Just keep talking about the entrance to the dungeon until they decide to go in, telling them that they see things that look interesting inside, or asking whether they’re absolutely sure they want to keep walking. See above – railroading. And I don’t want to get to the point where I’m saying ‘look, can you please just do the thing I planned for.’
  • Let them carry on the way they wanted to, but invent another fight that I hadn’t planned in order to force them to run short on spells eventually. See above – I don’t really want to keep forcing them into fights if they don’t want to.
  • Do exactly what I did, and let them carry on with what they wanted even though it makes me frustrated.
  • Something else, and if so what?