There are free tools online to read the barcode on the ticket, and the info there should match up with the written ticket details. If not, then it's definitely been altered.
It is possible to make a new barcode as well so that still is no guarantee against a fake ticket, only a lazy fake.
The barcode will just show the ticket number, which if unaltered from the base ticket used for the fake will match. 2d-Barcodes like that are numeric