The search() appearance/function does not work in web forms. Unless you have more than 50k or so rows in your CSV or are using slow devices, we generally recommend using select_one_from_file with a choice_filter which works exactly the same way as a select from a choice list in the form. You can use any kind of expression in the choice_filter column to filter the list from the CSV.
If you need to access specific columns from your CSV after you've selected an item, you can use list lookups with instance().