Strange session

I'm not prone to comment much about our gaming sessions but last Sunday one was kinda strange. First, let me do some recap. I'll try not to spoil the module.

A couple of sessions ago the group found, under the Tower of Magic, what it could be a magical way into where the simulacrum of Iggwilv might be. After learning how it worked they left for the city and came back with the magical means to use it and get there, but in the last minute they decided, although knowing that time was a pressing matter, to try another route. And so, they went into the Tower of Zagig. I must admit that, with their decision, they caught me off-guard and I had to make it all on the fly. They explored the tower ruins, killed several undeads, found a secret staircase and took their way down. Of all the traps and constructs I put in their path, none of them prevented the group to reach the crypts . Then I begun throwing at them several mummies which they managed to turn or destroy in what they called "Mummy frenzy". With that, after two really enjoyable sessions we reached last one.

When they entered a maze of corridors and rooms, a ghost appeared, warned them not to continue further and left. They just ignored it and pressed on. After a little exploration, they reached a couple of unscratched magically warded double doors... guess what? They decided to go the other way! What they found were clues that they were in a place that has been already plundered. Visibly forced doors, those once trapped had the traps jammed or disabled, niches desecrated, sarcophagi pilfered, pit traps marked on the floor, crosses and arrows marked on the walls, tunnels made to bypass heavily warded doors, etc. They even found the corpses of an unfortunate group of adventurers. When they finally realized there was nothing to be found and decided to go back to the double doors, there was no more time to play.

After the session my wife told me that it has been a bit boring, with no combat and only some saves made. I just said that the players, with their decisions make the game funny or boring. There were plenty of hints of what was going on. They just chose to ignore them, kept going and backed away (for a second time in the last three sessions) from what would have looked important to any adventurer.

I don't like railroading, but I confess last session I was tempted to do it. They're all experienced players and that's why I found strange what happened.