Unusual check-in issue at JFK last night

Debated where to post this, mods please move if not appropriate for "general discussion".
Just had a call from a friend to whom I'd recommended VS a while back (she normally flies BA) - her & a friend flew back from JFK last night. They were in Economy and booked on the VS10 departing 21:45.
Check-in was fine, except they were told they couldn't be be seated together, issued with boarding passes, then onward with luggage to x-ray. In the queue the security people were shouting out for "anyone on the 46 please come to front of line". My friend took a casual look at the tag on her case and noticed that it displayed VS46, however her friend's tag showed the expected VS10.
Panic set in and back to the check-in. A very matter of fact agent (no apology or anything) simply said that "the 10 has a two hour delay so I'll move your friend on to the 46 as well".
In a nutshell, they both ended up on the 46 and sat together. Baffles me how two passengers on the same reservation who check in together can "accidentally" be issued with boarding passes for two different flights?
Thanks
James
Just had a call from a friend to whom I'd recommended VS a while back (she normally flies BA) - her & a friend flew back from JFK last night. They were in Economy and booked on the VS10 departing 21:45.
Check-in was fine, except they were told they couldn't be be seated together, issued with boarding passes, then onward with luggage to x-ray. In the queue the security people were shouting out for "anyone on the 46 please come to front of line". My friend took a casual look at the tag on her case and noticed that it displayed VS46, however her friend's tag showed the expected VS10.
Panic set in and back to the check-in. A very matter of fact agent (no apology or anything) simply said that "the 10 has a two hour delay so I'll move your friend on to the 46 as well".
In a nutshell, they both ended up on the 46 and sat together. Baffles me how two passengers on the same reservation who check in together can "accidentally" be issued with boarding passes for two different flights?
Thanks
James