I've never heard of somebody getting fired for losing a piece of equipment so I think you can probably put your mind at rest there. It is likely however that this will be yet another reason for them to give you a rollicking for not being careful with the equipment. Probably a lesson to learn, never to rush around even when under extreme pressure as that is when stupid mistakes happen.
Is it in your coat pocket? I did that a few years ago, heard it bleeping on low battery at midnight!
I've 'lost' PDAs a few times over the years. They have eventually turned up always because I had put them somewhere stupid or someone else has done something stupid with them. It's very likely yours will too as they are of no use to anybody to nick!