It was most probably ‘found’ in the same place that all of my missing mail was consigned to. I have missed two important medical appointments thanks to Royal Mail’s inability to actually deliver mail to the addressee🤬
a 100 years is a long time , loved to know where its been all this time ,About 40year ago i sent a cheque to a catalogue Company, payment for a Coat , they never got it and it was never cashed …
You hear of some dodgy Postmen ,but its odd when letters dont get opened or Cheques cashed .
Maybe if the post box is full some may get stuck somewhere inside, with automation in sorting offices a lot could be trapped somewhere. Take precaution when sending a cheque, so that any alteration will be obvious.
My sister received a letter from our mum who had been dead over a year. Sis picked up the letter recognising mum’s handwriting , there was slso another letter I can’t remember if it was enclosed or separate but it apologised for the delay as a post man had been in court for stealing post and mum’s letter had been in his house with other stolen mail .
A surprise and a shock , upsetting and uplifting , a message from heaven 
Goodness Susan, as you say a mixture of emotions. 
A letter to treasure.
Now you know why it is called “Snail Mail”
It’s certainly a mystery…I have the feeling that this might be something that somebody has discovered under the floorboards .
Unlikely to turn up in a modern sorting office.
Charming story all the same.
Quite an intriguing story. Isn’t a bit odd that Royal Mail doesn’t give further information about what may have happened? They could, however, explain why it was delivered apparently without checking who is now living in the house although Royal Mail was aware that it was a special letter and that it can be reasonably assumed that not even relatives of the original addressee may still be living in the same house 100 years later? Given these circumstances, doesn’t Finlay Glen’s opening the letter appear in a different light then?
How amusing by today’s standards to see a letter addressed to a woman whose name does not appear on the envelop as the addressee.
I didnt know it was against the law to open a letter that not got my name on but my address ,
I would always open letters that have my address on .
I had a debt letter addressed to another name using my address… The Debt collecter was writing to everyone with this name it said looking for this person that owed money , I sent them a reply back and told them they didnt live at my address and anymore letters refering to them would get handed to my Solicitor.
I never heard from them again .
And I would still open a letter that as my address on …
At risk of going off topic there was a film that dealt with delayed mail.
An American film I’m sure, the mail bags were lost in a crash , years later the letters were delivered.
Not everyone was happy when they eventually got their delivery .