First, as people have stated on another recent question here, there may well be cheating by players in online poker. But what you're describing is not all that fishy.
You don't describe the pre-flop action or how many players were in the hand. You also don't describe the suits of your hand, the flop and the villain's hand, which I'd argue has at least a little bearing here, since flush draws can be very attractive to people and having even a back-door flush draw can make a difference between a call and a fold being correct. You also don't describe the relative stack sizes at the table, which are important in determining the odds a player would be getting to call you. All those things would help in determining just how crazy (or not) the villain's call was.
Next, you flopped a straight, which is a great hand on that board to be sure, but:
- It's not the nuts. AK is the nuts here, and if there was substantial pre-flop action, you can't easily discount that someone already has you beat.
- There could also be players with a set or two pair. Since that flop is rich in broadway cards, it's likely to hit many players' hand ranges. JT, QJ, TT, JJ, QQ are all hands that might both withstand a pre-flop raise and love this flop. All of these hands have draws to beat you.
- A hand like KQ has top pair and an open-ended straight draw, which is also a strong holding on this board.
- Any flush draw out there would be attractive. For example, top pair and a flush draw is often a pretty good hand. Might that have been what your AQ villain had? There are lots of outs for this player to beat you, even if he knows what you have. Any flush card, any king, a back-door full house, or the unlikely back-door QQ beats you.
- At lower stakes, people often love top pair and will take it to the river, no matter what you bet into them.
So, you have the case where you're not nutted, and the board is attractive to all sorts of holdings. You go all-in and you get called. Here's what PokerStove says about your odds. First, on a non-suited board:
Board: Qc Jd Th
equity win tie pots won pots tied
Hero: 84.032% 83.58% 00.45% 158864 864.00 { K9s, K9o }
Villain: 15.968% 15.51% 00.45% 29488 864.00 { AQs, AQo }
You have an 84% chance of winning the hand. That's pretty good, but your opponent has about a 1-in-6 chance of winning even so -- any K wins it for him, plus his back-door draws. Now, if the villain also has a flush draw (note the diamonds on the board and in the villain's hand):
Board: Qc Jd Td
equity win tie pots won pots tied
Hero: 55.063% 54.72% 00.34% 8668 54.00 { K9s, K9o }
Villain: 44.937% 44.60% 00.34% 7064 54.00 { AdQd }
In this case, the villain is getting amazing odds. He's got a 45% chance to win. It's almost a coin flip, and given the money already in the pot, it's unlikely to be a mistake for him to call you even if he knows exactly what you have.
So, you have a right to be disappointed in the result of the hand, but these things happen, and it wasn't even a big outlier. You might also question the wisdom of going all-in there given the number of other players in the pot and the fact that they were all likely to hit a piece of that board, but that's a question for another day.
Is it rigged? Maybe, but probably not. Did the guy get lucky? Maybe, but not that lucky. The more you play, the more you will encounter hands like this and worse. All you can do is get back in there and try to make good decisions with your future hands.