Anything is possible.
Last week I installed a new cylinder head, and radiator in a Toyota Celica. The car ran great for 2 days, then began stalling at idle. The MAP sensor went bad... Fixed that, and 2 days later the car started skipping at high rpm... The Ign coil went bad...
Point is parts fail when they want to, and this may confuse what you think is happening. The owners "buddy" insisted it was a fault in the new head. Just cause the last part you touched "appears" to be the fault, you have to remember everything works together, and parts fail when they want.
Check for spark when the bike won't start. also spray out the ignition cylinder (key set), w/ PB blaster. There may be dirty or worn contacts in there. I'd do all the switches actually. It's an older bike.