Heartbreaker

$160DS on PS, I never post hand histories, but had to post this one.

PokerStars Game #1567801096: Tournament #7057119, Hold'em No Limit - Match Round I, Level VI (100/200) - 2005/04/22 - 20:23:45 (ET)Table '7057119 4'

Seat #5 is the button
Seat 3: luvforty (5855 in chips)
Seat 5: ngala2 (3390 in chips)
Seat 9: misst74 (4255 in chips)

misst74: posts small blind 100
luvforty: posts big blind 200
*** HOLE CARDS ***
Dealt to misst74 [Ah Ad]
ngala2: folds
misst74: raises 200 to 400
luvforty: calls 200
*** FLOP ***
[3h 7h Qd]
misst74: bets 400
luvforty: calls 400
*** TURN ***
[3h 7h Qd] [2d]
misst74: bets 1000
luvforty: calls 1000
*** RIVER *** [3h 7h Qd 2d] [As]
misst74: bets 1000
luvforty: raises 1400 to 2400
misst74: raises 55 to 2455 and is all-in
luvforty: calls 55
*** SHOW DOWN ***
misst74: shows [Ah Ad] (three of a kind, Aces)
luvforty: shows [5h 4h] (a straight, Ace to Five)
luvforty collected 8510 from pot
*** SUMMARY ***
Total pot 8510 Rake 0 Board [3h 7h Qd 2d As]
Seat 3: luvforty (big blind) showed [5h 4h] and won (8510) with a straight, Ace to Five
Seat 5: ngala2 (button) folded before Flop (didn't bet)
Seat 9: misst74 (small blind) showed [Ah Ad] and lost with three of a kind, Aces

How could I NOT have seen that on the river? I did NOT see the straight, I thought I had the nuts, but even still, even if I HAD seen the straight I still would have called. How could I possibly put him on 4, 5??

4,5????

What a heartbreaker.