You need it for work, stupid.  
"Didn't I tell you about that, dear?? Oh, well....."
NBD.......

I keep mine in my office computer bag, at the bottom of the compartment with all the cables and batteries and other electronic junk.  It would be pretty hard to find it there.

If it were ever found, I would say it belongs to a club that I'm involved with in my civilian life that my SO is well aware of.  To reinforce my story, I wrote the club name on the phone.  If it's ever found, I'd say that "darn it, I had been looking all over for that stupid thing - how did it get in there?"

I would have to say it belonged to a friend or coworker and he left in in the car last time we played golf, went fishing, had a meeting, etc.  As long as the occurance was recent it should be believable.  I would also make sure to toss the phone right after it was found and get a diffent one in case it was found again.  Don;t want the same phone to be found twice.

Its just another old phone I'm saving to reactivate when we need another one at work.  "You mean it works and you can call on it?  Well I'll be darned."

Oh, and don't forget to clean out all the memories after your last date.  You don't want the little Mrs. calling the last # and getting Tornado Tilly's voice mail.

Admit nothing, deny everything, and immediately start counter accusations.

spare tire compartment of your car makes a great place to hide it, so does under the engine hood if you can get a case to protect it and hold it in place-disposable cable ties work great for that purpose; keep it in your locker at gym; keep it at work, always have ring tone set to silent