Notes

And here Kasa's point stands! He believes that Welcome Home was deleted and "lost" due to its infectious behavior! And like all viruses, they want to spread! Spread spread! So it started off with the simple envelope given to the original WHRP member! This is why they felt they needed to open it! With this, they then unintentionally let the WH go dormant and incubate, once again like a disease!!
With this, they kept searching and searching, possibly earning help from the other members and the exhibit worker! However, like all viruses, the incubation and dormancy ends! That's when the little story in the top of Staff Only happens! Where the member gets the dream of Wally with the phone when working on the exhibit! Where they start reporting they heard the constant ringing! If you look in that big chunk of text, you'll see that it says They're the reason it's so messy in those photos! Because they dug through and tore apart the place, trying to find where the constant phone ringing was coming from!
Of course, how exactly does this spread? The WBGS! (Weird Black Goop Stuff!) Its been here since the beginning, as the first instance we see it is the Joyful Family Portrait used as an example in the About Us tab! The WBGS must’ve been all over the envelope that the WHRP member received, and must have been the reason the WHRP started all of these insane behaviors!
Now enough back tracking! One of the letters in Staff Only shows that the WHRP Member must have figured it all out, and warns anyone that if “stuff starts to grow (WBGS??)” to return it! Along with this, they warn for all things to be touched with gloves only!