I'm afraid you'll need to strip the machine down and take the right side panel off to get the plate from inside and then fit the striker.
Depending on the build of your machine, you may have to release the rear panel and hob
top to remove the side panel.
Sorry, no easy way to do it.
Isolate the power to the appliance.
Take the screws holding the side panel in place out.
If you take the rear screws out (and the hob off a bit, if necessary) you can pull the side panel away to reach in to fit the parts.
It best if you take the panel off though, that way you don't damage the side panel.
Check it out, see what you find and get back to me.
Let me know how it goes