All search engines have no choice but to act on your DMCA complaint... even if the material could be public domain - they are really not overly concerned about someone infringing on your rights but protecting their own.
Search engines are in no position to prove or disprove your claim they merely wish to protect themselves from you filing a lawsuit of coercion.
If I filed a DMCA claim with Google, Yahoo, and MSN, and they ignore it you can be certain my lawyer will be filing against them and the likely punitive damage will be sizable.
Therefore, so long as you are certain that you physical wrote the text info, took the picture, video, audio, etc. is 100% worth your time to file and they will remove.
It is worth noting that the site owner can file a counterclaim at wish time you have 14 days to file court action and notify search engines or they will reinstate the information in question.