It’s not uncommon to remember the car but not the customer, there is a search option for that. Also, you may want to look for an invoice with a specific labor line or part on it, you can do that too.
Select History (F4), then when that screen opens up be sure to click on the “vehicle” tab. This will ensure you are in the right place to search.
You can use the “Word Search” to search for
Work Requested/Performed, Part Description, Notes, Invoice Ref# or Part Ref/Inv #.