What do you mean 1Ad doesn't import...import into where? Do you mean it doesn't export from Multibit into the .key file...that it isn't in your list of private keys. If you have 570 of them, then you could have missed it somehow.
It should be in there and then you should be able to follow my directions above to recover the BTC at that address.
The address where the change was sent is listed in the "request" tab in the original Multibit wallet file. That address is not included in the private keys exported by Multibit.
The private keys to that address simply aren't there. There is 0 possibility that I missed it as I cut the keys from excel file and pasted them into a new key file. All of the keys in the file have been accounted for. I've exported the keys to the original wallet several times and opened them in parallel in excel to confirm the entries are identical.
What could cause Multibit to skip the keys for a change address? I've never seen anything like this either...