How to recover iMessages sent to main phone number when using a different SIM card overseas? I am a U.S. AT&amp;T customer with an unlocked iPhone 6 plus, but am currently travelling through Spain and using a pre-paid Vodafone SIM card. 

One major problem I've run into: 

After inserting the new Vodafone SIM card, my AT&amp;T number gets deactivated from iMessage and all messages being sent to that number aren't being delivered. 

My questions are:

1) Will the iMessages currently being sent to my AT&amp;T number be delivered once I put my AT&amp;T SIM back in?

2) If not, what should I do so that I don't lose all of the messages that are being sent to my AT&amp;T phone number?
Apple stores iMessages on their servers only until they are sent to your device. Therefore, they will be sent to your iPhone once you put your original SIM back in. 

Another option would be to add an email address to your iMessage account and then even messages sent to your original number will be forwarded to your phone with the temporary SIM in if it has the email address associated with your iMessage account.