Missing PCA key

Ugh! So yesterday at the end of my (day) shift, the MD ordered a PCA. I am new on my unit, so to assist me, another nurse grabbed the pump, key, and medication & had me program the PCA while the other nurse verified that what I programmed in matched the order. I remember having to turn the key to "program" to enter the dose, etc, and I remember having to turn the key to "lock" to start the pump. Unfortunately, I have absolutely no recollection of what happened next, in terms of the key itself. Anyway, after watching me hook up the line to the IV, etc, the other nurse left the room.

First thing the next morning I get a call - the PCA key is missing! I know 100% for sure that I did not return the key to the Pyxis (don't really know how to do that yet - accessing the key drawer involves a lot of unfamiliar steps with the touch screen, so I would have had to ask for help, etc & I would remember that). The other nurse says that s/he did not return key to the Pyxis herself, and s/he says s/he did not take the key home by accident. I drove to work and searched the patient's room, but the key was not there. I am 100% positive I did not bring the key home by accident. The charge nurse told me s/he will write an incident report.

I feel awful, and I feel stupid, and I'm also very worried.

So what's going to happen next? Will I possibly get fired for this? I can't go into detail, but it's extremely extremely extremely unlikely that the patient found/tampered with the key (in the event that I left it in the room) & the history on the pump does not show that anything out of the ordinary happened with the dose administered via that pump.

Thanks for listening! Lesson learned, I know, I know. . .