If you chose to Cross-List your classes and your students have lost work in Canvas, there is no way to recover it.
If you do combine sections, please take the following steps to protect the privacy of students in the individual sections:
Disable the “People” menu option that allows students to see the entire course roster for all sections. Instructions for disabling a course navigation link
If you use Discussions, create separate groups for each section of students and assign each discussion to the separate group.
When sending messages through the Conversations Inbox, always choose to “Send Individual Messages” so that a group reply is not possible.
Whenever you share or cause to be shared student information within a course or section(s) ensure that no student within the course or section has invoked a FERPA hold on all of their directory and non directory information.