Welcome to the forum!
TfL take misuse of Freedom Passes very seriously. They don't really need to research the journey history as the single incident where you were caught is all they need.
TfL will send you a verification letter which typically takes a couple of weeks to arrive. This letter will ask you to confirm or deny the offence and will ask you to give any mitigating factors. It is extremely important that you reply to this letter. Responses to the letter are given 'under caution' i.e. 'you do not have to say anything but it may harm your defence if you do not mention when questioned something which you later rely on in court.' TfL has three choices:
1. Drop the case altogether
2. Prosecute you for fare evasion (highly likely to be a prosecution under the TfL Bylaws)
3. Give you a final warning
TfL don't normally offer out of court settlements, which we often see with National Rail operators. I would expect them to persue a prosecution under the TfL Bylaws where misuse of a Freedom Pass is detected but there is always a chance that you miht get lucky.
Feel free to post a copy of the Verification Letter when it arrives (but do redact any personal details from it before posting it) along with your draft reply to it and forum members will be happy to proof read it for you.
It might also be worth having a reasd of TfL's Revenue Enforcement and Prosecutions Policy: