I ran into an issue the other day and wanted to ensure that I shared it out there. In a Log Shipping scenario, you can occasionally run into a corrupt transaction log backup. This causes the database to stay in restoring mode (as mine was previously in a standby/read-only state for reporting), but requires the next LSN to be restored, which you don’t have.
In this case, it went overnight and was out of sync a ways, but at night I do a differential backup of the database. By restoring the differential backup with norecovery to the log shipped database, it allowed me to continue restoring with log backups from that time on.
Hope that helps anyone in the www realm, it is a nice save since databases can be large and the initialization could be very impactful.