I've lost a gold brick, what have you lost?

A human head.

Huh, this explains a lot...

1 pound = a Guinea Pig
1.5 pounds = a dozen Krispy Kreme glazed donuts
2 pounds = a rack of baby back ribs
3 pounds = an average human brain
4 pounds = an ostrich egg
5 pounds = a Chihuahua
6 pounds = a human skin
7.5 pounds = an average newborn
8 pounds = a human head
10 pounds= chemical additives an American consumes each year
11 pounds = an average housecat
12 pounds = a Bald Eagle
15 pounds = 10 dozen large eggs
16 pounds = a sperm whale's brain
20 pounds = an automobile tire
23 pounds = amount of pizza an average American eats in a year
24 pounds = a 3-gallon tub of super-premium ice cream
25 pounds = an average 2 year old
30 pounds = amount of cheese an average American eats in a year
33 pounds = a cinder block
36 pounds = a mid-size microwave
40 pounds = a 5-gallon bottle of water or an average human leg
44 pounds = an elephants heart
50 pounds = a small bale of hay
55 pounds = a 5000 BTU air conditioner
60 pounds = an elephants penis
66 pounds = fats and oils an average American eats in a year
70 pounds = an Irish Setter
77 pounds = a gold brick
80 pounds = the Worlds Largest Ball of Tape
90 pounds = a newborn calf
100 pounds = a 2 month old horse
111 pounds = red meat an average American eats in a year
117 pounds = an average fashion model (and shes 5'11")
118 pounds = the complete Encyclopedia Britannica
120 pounds = amount of trash you throw away in a month
130 pounds = a newborn giraffe
138 pounds = potatoes an average American eats in a year
140 pounds = refined sugar an average American eats in a year
144 pounds = an average adult woman (and shes 5'4½")
150 pounds = the complete Oxford English Dictionary
187 pounds = an average adult man
200 pounds = 2 Bloodhounds
235 pounds = Arnold Schwarzenegger
300 pounds = an average football lineman
400 pounds = a Welsh pony