Bone mets to only one site and no other signs of mets?

[SandyBB]

Have any of you heard of bone mets appearing in only one spot at first discovery/with no other evidence of metastatic spread?

I was diagnosed as stage 2B in Sept 2003, with 3 positive nodes. Had partial mastectomy, and finished aggressive treatment in April of 2004. Then in the fall of 2005, my onc called and told me she wanted to start me on Herceptin - which I did in Oct of last year. Two months ago, I experienced bad pain in my rib area, right under where my cancer was and I had no recollection of any recent trauma to the area. My onc did x-rays, which were fine, but the bone scan showed significant uptake on one rib (exactly on the spot where I had marked the pain). My two prior bone scans in 2003 and 2005 were totally clear (so it isn't from past trauma). She then ordered a Catscan which was clear, and blood tests were fine - including tumor markers and enzymes.

So - my onc feels that the uptake on the bone scan is most likely NOT evidence of bone mets because it is the only site in my body and she says it is highly unusual for metastatic disease to evidence itself in only one isolated location.
I am waiting a total of 6 weeks and then will have a new bone scan done to see if the spot still lights up. She strongly feels it will not and that I must have bruised the area and not remembered doing so.. if it does light up again, and there are additional spots - it is bone mets. If only the rib still lights up, she said I would probably have to have the rib removed for biopsy (a needle biopsy of ribs is unreliable).
As most all of you know, the waiting is the pits! And I can't help but be pessimistic - I know I did nothing to bruise the area (at least I think I didn't!)and what are the odds that it would light up right under where my cancer was?
Have any of you heard of bone mets appearing in only one spot at first discovery/with no other evidence of metastatic spread? Any of you had a bone biopsy?