How a government employee travels
Every government employee (I don't know if this applies to very high government officials, though) must obtain what is called a travel authority from a superior. If the travelling employee is a rank-and-file government functionary, the authority comes from the superior officer that has control of your department's budget, probably from a department or regional director. I used to approve these babies for the department I headed. If you are a director or higher, your travel authority probably comes from the head of adminitration and finance of the entire agency.
In case of foreign travel, this authority comes from the Office of the President. An official travelling abroad without such authority is a ground for administrative action.
In the case of the Commission on Elections, the travel authority of a regional director comes from, you guessed it, a Commissioner, most probably the commissioner-in-charge for that area, or the Chairman.
Basically, the forms filled up by travelling employee consists of the travel authority, the pre-determined day-to-day itinerary (which is very detailed, including the taxi ride from your house to the airport, the taxi rides commuting around the destination area and the taxi ride from the airport to the home), the expected output and the amount requested (for the travel expenses, tickets and the employee's per diem) in voucher form.
Upon approval, the funds requested is released to the employee to pay for plane/boat ticket, etc. and employee goes about his merry ways.
After the travel, the employee submits a travel report on the output of his/her travel and the liquidation of the funds released to him, with annexes (such as the plane ticket, boarding pass, terminal fee ticket, etc.). Failure to liquidate is likewise a ground for administrative action (because the employee handled public funds), as well as an automatic salary deduction of the amount released.
All of these documents are submitted to the Commission on Audit for, you guessed it, audit purposes.
Oh, and by the way, every travelling employee likewise applies for travel/accident insurance with the GSIS. So, some evidence of an employee's travel can also be found there.
Hence, you can check Zuce's story with the Comission on Elections, the Commission on Audit and the Government Service Insurance System. So if someone is planning a cover-up, he has to have access to all three agencies. Pretty easy if you are powerful enough, I guess.