It's possible the 'Ejector Plate' on the left side of the bolt fell out when the bolt was out of the gun. It just drops in place in the bolt and then slides forward maybe 1/16" and is held there by a couple machined tabs engaging cuts in the bolt.

It's captured when the bolt is assembled in the rifle and can't go anywhere. But if you have the bolt out of the rifle,,the plate can easily slip out of it's machined recess and fall away un-noticed.

Simple to see if it's gone,,just take the bolt out and look at the left side of it. The plate is about 2" long, narrow and with a tail on the back end.

If it's missing,,the interface between the bolt latch and the action bar is gone,,meaning you can't unlock the action using the unlocking latch button on the bolt.

Usually, in that case,,dry firing the rifle will allow the action to be opened.
But it sounds like that is not the case here.

The only thing I can think of happening then is that the firing pin was already down/fired position when the bolt was reinstalled in the rifle.

When the bolt is replaced in the recv'r for reassembling,, the firing pin must be cocked.
If it isn't, the bolt will not interface and engage with the action bar (pump action bar).
I'm thinking perhaps that is the problem,,or perhaps one problem.

Remove the bolt and while checking for that Ejector Plate,,also make sure the firing pin is cocked. If it isn't,,do so.
Simply push back on the firing pin sear shoulder at the front bottom edge of the bolt. Push it back into the bolt till it engages the sear and clicks.
Use a small screwdriver or the tip of a small dia punch.
Now the firing pin is cocked.

Here's a schematic of the Mod 14,,,a full schematic including the bolt.
(Numrich and others generally print only the first page and that leaves off the detail pictures of the bolt which isn't helpful at all!)

http://www.remingtonsociety.org/forums/viewtopic.php?t=2093

What I called the 'ejector plate' above,,they have tagged as just 'Ejector',,part #25

The 'Ejector rod' part #26,,is what I always refered to as the actual ejector in these.
Just my part terminology vs theirs I guess.

Numrich used to have the Ejector Plates (Ejector #25) for sale. I had to replace a couple over the years that were missing.
They used to have two different styles listed. One for the Model 14/141. Another for the 14 1/2.
...The Model 14 1/2 uses the exact same #25 part as the Model 14. Nothing special about them.

What Numrich had were a bunch of Ejector Plates that were incomplete as far as their machining status. Probably old stock bought from Remington and Numrich just assumed they were for something different.