Contacts on SIM-Card are very limited -- so they e.g. can only store one phone number. Your phones / Google contacts, however, use a much enriched format, where you can store additional information like multiple phone numbers and even pictures.
Naturally, both formats are not 100 compatible. When exporting your contacts to SIM, information must be cut down to fit that format. That was when you lost your additional information. So no way to get that back -- it was gone the moment you overwrote your data doing that import.
The only chance left is using "forensics methods" -- in the hope the "deleted" data has not yet fully been overwritten. However, that would require root access to the device: You need to locate the contacts database (it's most likely named contact2.db, and will probably be located below /data/data/com.android.providers.contacts/databases/ -- the location might be different with some devices (e.g. Motorola uses a different provider for this). You could copy the databases from this directory to your PC, and investigate deleted entries with a HEX editor -- but that's no easy job for someone not used to it...
I know it's too late now for that -- but it might help you next time: To backup/restore your contacts, the contacts app offers an export to VCard format (.vcf) which it of course also can read back. This way all information is kept.
