Because Matthew Gray Gubler busted his knee while partying with his 500 Days of Summer (2009) co-stars, poor Dr. Reid had to get shot in the leg in this season opener. Note how he just happens to be sitting throughout, before being shot.
As is customary on all or almost all motion pictures and television episodes, all of the phone numbers shown in what is supposedly Aaron Hotchner's personal address book have a "555-" prefix. Except for directory assistance, that prefix is almost never used for a real telephone number, and thus is convenient for phone numbers depicted in cinema fiction, so that a real customer won't be harassed if the person's number were publicized.