Nope. Letter gets returned.My paranoia has eased somewhat... I am still not collecting said letter.
I was reading somewhere ... if you ignore a registered letter, it can go against you, if its a legal letter.
Its assumed you got the letter.
They can resend or they can deliver personally.
You can check the tracking number (usually on the failed delivery notice) and see where it was posted from. Not very accurate, but can be informative if from a county other than Dublin.
I know one person who sent a registered letter of a summons disguised as a birthday card with "pretty envelope" - worked a treat