Not finding anything in STL city cemeteries, but here are a few other leads for you:
Missouri Digigtal Hertitage has two results under this spelling for pre-1910 death records. Both are shown as buried at St. Peter's Cemetery in Normandy (St. Louis County).http://www.sos.mo.gov/archives/resources/birthdeath/dresults...
St. Peter's Cemetery has an on-line search function. I didn;t find any burials with that exxact spelling, but I did find a lot wirth some SIEWECKE burials:http://www.stpeterschurch.org/cemetery/cemetery_SearchResult...
You might try a couple other alternate spellings and see what you come up with.
Also found a couple of Post-Dispatch obituary index entries with the spelling Sieweke:http://www.slpl.org/slpl/gateways/article240117800.asp
Not quite what you asked for, but maybe some of it is helpful.