I suggest you take your request for records up a few levels at Lyft. Ask for a supervisor, and then maybe that person's supervisor, etc.until you get the information you need. It seems that Lyft would a least keep records of the transactional fees, or tell you how they were calculated.
If all efforts fail, reconstruct your income and expenses as best you can. If the IRS should send you a letter with questions, just explain what happened and the steps you took to recreate the income and expense figures. They can be very reasonable.
