this may be splitting hairs, so to speak, and I would defer to my Florida Colleagues, but it would seem that it depends on what you are referring to, as to whether it can be used against the defendant later in the lawsuit. There is a difference between a party arguing as a whole that you did not have a contract, and he/she taking a position in a sworn affidavit as to a point of fact. For example, if a party swears in an affidavit in support of a motion to dismiss that he did this or that, and then later on at trial denies doing so, you should be able to use the earlier affidavit to impeach that party's credibility.
A motion to dismiss should be directed to the Complaint's deficiencies. The Motion should not have contained "evidence", since the judge can only look to the contents of the Complaint to see if it sets forth a proper cause of action. On a Motion to Dismiss, the judge does not rule as to the truth of its allegations, but whether the claim is properly alleged.
Unless the Motion was verified, which is to say under oath, the contents of the Motion will not be evidence. True, the jude may think it a little weird that there was a change in position, but if the defendant was not represented when the Motion was made the judge will understand that the defendant may have been educated by an attorney and now understands better what transpired.
I hope you found this response to be of assistance. This response shall not be considered the rendering of legal advise but instead a general response to a general question. While Avvo is a wonderful resource, nothing can be a substitute for an in-depth consultation with an attorney in the jurisdiction in which the law is to be applied. This response shall not be deemed to create an attorney-client relationship, nor shall it create an obligation on the part of the attorney to respond to further inquiry from the questioner.
I agree with the other comments; motions to dismiss should not introduce evidence. However, I urge you to consider consulting with an attorney. If you're dealing with a motion to dismiss, it is best to have an attorney help you get past it. Good luck.
To schedule a consultation, call my office at 407-965-5519. I am licensed to practice in Florida only. My answer does not create an attorney-client relationship, nor does it constitute legal advice. Proper legal advice can only be given after learning all circumstances and conducting a comprehensive examination, including being able to ask questions, and cannot be given just from reading one question on an Q&A board such as this.