Hi there. Some emblems are restricted to only being accessible on the platform account they were originally earned or claimed with a code and cannot be shared via Cross Save linking or visible from Collections on other accounts. Since you are using Cross Save, try logging into the account you originally played on when you got the emblem to see if it appears in your Collections. If it does, then it confirms that is one of those emblems and you will have to use that account to get it. If the emblem doesn't show on any of your platform accounts, that would suggest you originally got it through an 'account recovery' to get a copy from someone else before Bungie implemented this restriction. If that is the case you will not be able to get it back.