Triage vs Backlog vs Assign to next iteration

The backlog in an agile project should be the collection of all work that needs to be done on a project.  Generally, all your higher level or as-of-yet-unplanned work items will be in the backlog.  Are you using any sort of Priority ranking or value?  When planning each iteration, you can sort the items in the backlog by their priority, and move the most important ones into the iteration you are planning for (this can be done pretty nicely with dragging and dropping from a Plan View).

I believe the standard agile approach here would be to set the item priority as high and place it in the backlog.  If you are already assigning items to future iterations, then you could put this item in a future iteration where you will have time for it.  Setting the owner, priority, and planned for attributes are what the triaging process is, so you should also move it into a triage state when you decide what to do with it.