If all you did was restore a recovery-made-backup, I don't think that will restore original baseband and stuff. If this is how you got back to stock, that means that although you are running stock BLU-Android, you are still using the broken L100i incompatible baseband.
I am not sure if this phone is compatible with ODIN, but if it is and you can find a tutorial on how to restore your L100a back to stock with ODIN then this is what you want. I am not sure what ODIN stands for, but it's a download tool used for not only restoring a phone's android operating system back to stock, but the other things that a plain old recovery-backup doesn't cover like kernel and baseband. ODIN requires a Windows PC with the correct phone drivers installed. So in this case you need the your phone's drivers from BLU on your computer, so that when you plug the phone in it is recognized as a BLU Life. Again, I am not sure if there even is an ODIN image for your phone since generally BLU phones are not that popular on XDA, but if there is then follow the instructions and use that to restore back to stock instead of just using a recovery backup.
IF YOU DO FIND AN ODIN IMAGE FOR IT, MAKE SURE THAT YOU DO NOT MAKE THE SAME MISTAKE OF INSTALLING THE "I" VERSION INSTEAD OF THE "A" VERSION! MAKE ABSOLUTELY SURE THAT THE ODIN IMAGE IS THE
EXACT ONE FOR YOUR PHONE!!!!
EDIT: I just re-read your post and realized I didn't exactly answer your question. Sorry about that.
You should do the ODIN thing I mentioned above, just to make sure that you are on the right baseband. However I do not think this restores your IMEI as well. I Google'd how to restore a lost IMEI on an Android phone and got a couple articles on how to do so. One of these articles tells that CHANGING THE IMEI OF YOUR PHONE IS ILLEGAL!!!!! However It doesn't sound like this applies to you according to what you said, because you are only trying to restore a lost IMEI number, not change an already existing one.
Have a look at
this article.
Good luck! :cyclops: