LYRICS (From the Valve ARG wiki):

INTRO (Before The Song Begins):
Hehe.
1, 2, 3, 4...
 [bad word] 
I don't know a cave from a hole in the ground
I wandered an age through a cool and dark cage
Tried finding my way by touch, taste, sense, sound
(1st time) But no way out of [bad word]  as the sin is on stage
(2nd time) But I'm here and I hope I won't see old age
(3rd time) But I figure the solitude's my only wage
(4rd time) And long past the point of pretending to rage

VERSE 1:
I wonder what happened up there to my [bad word] Left parked with a load, no doubt long since been towed
I never expected to have such strange luck
I should have obeyed what that road sign forebode

Cavefish is delicious, but only if cooked
You'll mess it up bad, well let's leave it at that
I've eaten whenever, whatever I've hooked
I'd kill for the thrill of a meal with some fat
 [bad word] 

VERSE 2:
I don't know my soul from a hole in the dark
I'd wake from my sleep and I'd silently weep
I once knew a girl who loved me as a lark
My pain, she explains, is what made me so deep

I thought I was ever so lonesome at home
It needled at me until I couldn't see
The forest for trees nor the sea for the foam
And I took up the job that was all absentee
 [bad word] 

VERSE 3:
The miles and also the hours were strained
Kept my hands on the wheel, it was solid and real
And wind blew and snow fell and [bad word] and rained
And I drove through it all but found I could still feel

Inspire me world, I was writing a song
Saw a sign for the cave, thought "artistic" and "brave"
I grabbed my guitar and I moseyed along
and though I hate to state it, I entered my grave
 [bad word]