Probably this problem could be regarded as a bug, but in the other side, a side note (if you'll excuse the repetition) jumping to the next page or making a page break of the main text do not have sense at all. It would make more sense adjust the side note manually in these cases.
For notes occupying the bottom margin, instead of
\foonote you can use
\sidenote than have an optional offset argument, so you can control the vertical position as in the example: