If the switch was stuck it's probably corroded, if it's corroded it's more than likely not making contact to earth. No earth and the alarm thinks someone's opened the bonnet. I would remove the switch and clean the contacts that make and break contact when you open and close your bonnet. Then test with a multimeter, between the terminal on the back of the switch to a good earth. Also check the terminal that plugs onto switch and make sure it's free from any corrosion. Check the wire hasn't gone all green and mucky, it may need cut back and reterminating. Does it have an after market boot switch to activate the alarm?
Surely a Clifford alarm has some sort of indicator, (LED on the dash or the hazard lights pulse) to indicate which sensor/switch has activated the alarm? Most alarms normally have something to warn you that the alarm has been activated when you unlock the car, and which sensor/switch activated.
Does the manual say what model alarm you have?