FB message failed to send, but has been 'seen'?

[AnotherAuthor]

So the other day I sent a fb message from a computer, it was 'seen' by the recipient an hour later but they haven't replied yet. When I view the messages on computer or on mobile everything appears normal.
But I have a brick phone and on the proper fb mobile app that I downloaded it appears normal, however on my inbuilt fb thing on the phone it says 'message failed to send' right under where it says the date I sent it, and then 'seen at xyz'. But if it did, how did the other person see it? And why doesn't it say anything on my computer? Which device should I trust? Has it actually been seen?

[abin]

if you have just types a message and due to some problems like in internet connection it cant be send to the typed one the it apppears that "message failed to send".

but when your message has reached to the typed ones and it has appeared to its inbox then it apperas
as"seen"

[KJBALAJI]

the recipient has seen ur message..due to some problems in internet or in ur app..it displays like this..

[Daniel]

If it Says Seen At Than The Person probably Has Seen it its Also Possible That The Person Could've Seen it than Remarked it as Unread Which Takes That Away