Anyone have lost in the mail invitations?

We were very careful in double checking invites and save the dates. Two of our STDs got lost in the mail. My step sister who asked my step mom if she was invited to the wedding or not and one of my FH's cousins who both he and I are super close with and she helped with my shower, she actually asked at my shower that she helped put together if she was invited to the wedding or not (obviously of course they were both invited, they just didn't get their STD). I just found out today that 2 of my cousins didn't get their invites. My aunt texted me asking if her two kids were invited (they both received an STD). My cousins have a different last name than my aunt, so if some of the invites got lost, they would have been in a different section alphabetically. I double checked my invite list to the invites we had and everyone was accounted for. I'm just asking, did any other brides here have invitations that got lost. Did your family automatically assume bad intent (they were given an STD or included in other wedding activities and assume they aren't invited to the wedding, as opposed to something was lost in the mail), what was your response for bouncing back from that? I'm also now paranoid that a section of our invitations were lost, do you just wait until the RSVP date, or did you try to do follow up, just to make sure everyone got their invitation. Right now, I'm worried that every guest who has a B starting their last name (the letter that my cousins last name begins with) never got an invitation, and I'm only hearing about this through my aunt, because she would obviously be confused about her kids getting a STD, but not an invite. We've started to get some RSVPs in, but we actually haven't received any with B as the last name. It could just be that people still have 4 weeks, but it does make me nervous that more than the two were lost. I just don't want people to think they got an STD and are not invited to the wedding. Is my family the only one who goes to, oh you aren't really invited to the wedding, or do your families assume they're invited and just say to you that they think something got lost in the mail.