It’s a reference to an entry in the webcomic series Ctrl+Alt+Del. The female lead has suffered a miscarriage, and this particular entry in the comic, titled Loss, depicts her boyfriend’s journey through the hospital, entering the front door alone, talking to the receptionist, talking to the doctor, then standing at her bedside.

Ctrl+Alt+Del competes (competed?) with Penny Arcade, it’s normally a lighthearted junk food entertainment kind of webcomic aimed at a gamer audience, that SUDDENLY slammed into very heavy material, and then SUDDENLY slammed back out of it. The comic became very widely mocked for the tone whiplash, and one notable form of mockery was making increasingly minimalistic representations of it, often with a “you just lost the game” kind of intention, ie how minimalistic can you go while still reminding others of the comic. A common depiction might be I Ii II I_ (one man standing, a man standing and a woman sitting, so she’s shorter, two men standing at equal height, and then a man standing and a woman lying down) but now :.|:; is even more condensed while maintaining the four panel arrangement.

This is a meme from 2008; it’s been going around awhile. So to those who have been long familiar with the meme that graphic kind of works like a hieroglyph or kanji character; it’s a very simplified depiction of something that carries a sound/concept. You kind of read it as the word “Loss.”