If you've "turned over" the filename counter in your digital camera by shooting more than 10,000 frames, there's a chance that file matching during Photosmith's Lightroom sync may not work as expected. We've anticipated this situation, and allow file matching between Lightroom and Photosmith to do its thing by utilizing criteria other than just filename.
In Lightroom, go File -> Plugin Manager -> Photosmith plugin. About 1/3 of the way down, you'll see a section titled File Matching. Make sure you have date/time option checked, as well as any other settings that might be applicable to your specific workflow.
We go into better detail in Section 18.104.22.168 of our Knowledge Base.