lost collected email addreses

Based on this: https://help.yahoo.com/kb/SLN36803.html 

Note: If contacts appear to be missing after you've migrated, these may have been categorized as "Collected addresses" in your Comcast.net email account and not saved to your Address Book. Please also check that the missing contacts were not instead saved to a third-party address book or contact list, such as contacts stored on your mobile device or in a third-party email application like Outlook.

Based on this, since they are not official entries in your Address Book, they do not get migrated over.