I can't imagine that they'd be selling multiflora. If a plant was grafted on multiflora and then died it is possible that the root stock came back instead.

My other thought is that perhaps it could be Sally Holmes which is a very popular 5 petaled white rose.

The plant you bought died and you got rootstock. But most of the growers use Dr Huey which is a open red colored blossom with yellow at the base

If you just bought it pure Rosa multiflora would not be in bloom now, and the long, arching first year canes would have had to have been whacked back to fit a blooming sized plant into the usual retail situation - unless it was trained onto a trellis or other support and sold as an established climber.

Except where an R. multiflora seedling variant might have come up as a Multiflora rose, that is one producing re-blooming bush growth instead of rambling. But it is much more likely that you have bought one of the hybrid roses that may often have R. multiflora in their parentage, resemble it to varying degrees. One looking generally like R. multiflora (whatever its actual parentage, which I would have to look up) that was at several outlets here this year was Gourmet Popcorn. Another one that tends to be seen at independent garden centers is 'Ballerina'. But there are many possibilities, the R. multiflora appearance - with more or less conical heads of small white or pink flowers - is not rare among garden roses, both old and new.

Here is a link that might be useful: How can I identify a mystery rose?

This post was edited by bboy on Tue, Dec 31, 13 at 15:20