An Ignored Document

A word on Talmudic methodology:

There are two types of questions on a text.

One type of question is on what it DOES say. Maybe there is a contradiction from a different source or perhaps the logical is internally flawed or a myriad of other problems one can detect with a discerning eye.

Another category is questions on what the text DOESN'T say and trying to understand the omission.

Case in point: Under certain circumstances the Rabbis uproot and dissolve the marriage of a man and a woman. The gemara wonders what the mechanics of the dissolution are. Normally we need a get to end a marriage but here without a get they "get" out of the marriage. Says the gemara [in ksubos 3a; gittin and yevamos as well] "I understand how we can uproot a marriage that was created through the means of a monetary gift [קידושי כסף] from the man to the woman but how do we uproot a marriage that was created with ביאה?"

Question on what IS written - Why is it so simple for the gemara to understand that we can uproot קידושי כסף but so puzzling to understand how we can uproot קידושי ביאה? On the surface if the Rabbis are invested with the power to uproot kiddushin then it should apply equally to כסף and ביאה yet the gemara differentiates between the two.

Question on what ISN'T written: Here the text CRIES out - There is a third way to marry a woman and that is with a document [שטר]. First of all - do the Rabbis have the power to uproot a marriage created with shtar? More importantly - HOW COME THE GEMARA DOESN'T BREATHE A WORD ABOUT IT? It is SOOOO obvious!! The gemara discusses כסף and ביאה and ignores the "elephant in the room" - שטר.

WHY????????