Where's #4? I need your advice.

About a week ago I posted about three PWE from Wes, the author of Jaybarkerfan's Junk.  Wes numbered the back of each one, which makes it easy for me to know which one to open first.

Generally, I just open at will and don't think about it, but this new numbering system has me somewhat bamboozled.  I'm trying my best to maintain order and civility during the course of Wes' most recent barrage.

Here's what I've received on Monday (1/27):
PWE #6, postmarked 1/23, received on 1/27
and
PWE #7, postmarked 1/24, also received on 1/27.

Huh.  I've already cracked open #1, #2, and #3.  Now I have #6 and #7?

Yesterday (1/28) I received two more:
PWE #5, postmarked 1/22, received on 1/28
and
PWE #8, postmarked on 1/25, received on 1/28.

There's three days difference on the postmarked date, but the PWEs were delivered on the same day?  Seriously? It's 2014 and this still happens?

The better question is... "Where's PWE #4?"

As a high school teacher each spring the staff is on the lookout for the graduating seniors' class prank. I'm often asked by students what was the best prank I've heard of and I always refer back to the same story: Three pigs were let loose in a school and they were numbered 1, 2, and 4. Imagine the ensuing chaos as faculty, staff, and administration try to round up the pigs!  And then when things settle down, the confusion sets in, "Where's pig #3?"

 Perhaps you've heard of that one?  Some say it's urban legend. Regardless, I feel like I'm living it PWE-style.

Should I continue and open #5?  Or should I maintain my patience and wait for #4?  Following the above data, I can assume that PWE #4 was postmarked on 1/21.  It miiiiiight show up in today's mail, 8 days later. 

What if there is no #4? 

What would you do?