Here is a message that I received from Sheet Music Plus after I wrote to them about the situation:
Hal Leonard Legal is aware of this issue with this website. They seem to have only have the sample pages, not your full pdf.
For now, I recommend submitting a DMCA notice
Please submit it to the website owner, the website hosting company (If you know it) and CC us.
Based on this experience, it is prudent for composers to periodically do an internet search on several of their music titles and see what comes up. That is how I discovered that my music was at those two sites.