I have had a similar problem on my VRF1200FA recently. Mine came loose and then the push button dissapeared whilst out riding, it was expensive to replace as I had to have the whole left handlebar rubber grip and new push button switch assembly fitted.
When mine came loose I think I had lost the back half of the two part plastic handlebar clamp on which the push button switch is mounted. Then I think the switch top somehow came off.
Your warranty should cover you for a repair.