Hi,
The answer is maybe.
If you have not seen them yet then the answer will be no.
Basically if a device is Registered with iMessages with either an iPhone Number or and Apple ID it will get the iMessages.
If that device whilst registered is Off line fro whatever reason then it will get the iMessages when it is connected to the Internet again.
For me the longest that I have done this is over 7 days.
I have seen 1 post each for 9 days and 11 days but both were around the time the iMessages server had an issue and may have been related to that.
There does seem to be a point when the iMessages servers decide they cannot wait any more and the iMessages is deleted from the server.
There is a "known Issue" on iPhone whereby the iPhone Number become unticked in the Send and Receive section.
If this is not noticed the Number eventually becomes de-registered and you no longer even get the Sync version on the Mac.
It is less common that a Mac end s up in this state but it is not impossible.
Basically an iMessages is divided (copied if you like) so that an individual one can be sent to each device that is registered.
They are then sent to each device after it has uniquely logged in.
This means iPhones generally get all iMessages as they are On all the time with little, if any, breaks with the Internet.
The "Copy" for the Mac can therefore be delayed if the Mac is Off Line.
There is no way to access the "copy" for another device and "redirect" it to another.
The process of delivery is a push. The Servers Send them or at least try, again and again until they are accepted.
As I said there is a time limit to this.

8:40 p.m. Friday; September 4, 2015
iMac 2.5Ghz i5 2011 (Mavericks 10.9)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad