I haven't used a .50 for moose, however a local guy did, using, I think, 120gr. 2F. The moose dropped in his tracks, which is not normal. He was double lunged. You do not want to hit any bone in a moose with a .50 or .54 for that matter, however I'd expect either to punch through an on side rib and still double lung the moose. The ribs can be up to 1/2" thick, are rubbery and move when something hits them - they aren't ridgid.
I was about 800 yards away, when a guy shot a moose at a lasered 170 yards with a .54, .535" ball and 100gr. Pyrodex. The ball double lunged the moose (centred the heart as well) and came to rest against the hide on the off side. The moose ran like it was stung bya wasp, but dropped dead in 40 yards, mid stride.
Note that when shooting small bores, less than 20 bore, moose will usually give no sign of being hit by a round ball, or slug from the same gun. Note that slugs from 48" or slower twists do not normally travel in a straight line inside a moose, therefore your lung shot might actually be a gut shot or flesh wound as the slug usually turns on impact. Either way, ball or slug, the moose will usually take off as if scalded. There will be no blood as the tissues cover the small slit in the hide. there may be cut off hairs on the ground or snow.
If they run out of sight, same goes for deer, you have to give them time to sicken, lay down and stiffen up. 20 to 40 min is usually OK- but not always. If hit behind the diaphram, double those times - at least. Elk can run 10 times farther before stopping, even if not pressed, but moose are babies and usually lie down within 50 yards if not pushed. (pressed or pushed-same deal)