I highly doubt you were cheated.
The straight martingale is one of the riskiest betting systems any gambler could use. Any gambler who ever has used it with any regularity could tell you his own hair-raising "impossibly unlucky" tale of why he gave it up for more conservative methods. Here is what happened to you:

1. You bet $10, and lost.
2. You bet $20, and lost.
3. You bet $40, and lost.
4. You bet $80, and lost.
5. You bet $160, and doubled down on your 11 vs. the dealer 8, and you lost.
6. This double loss required you to place a next bet of $480, which you then lost.
7. You placed a bet of $960, and split your 8s vs. a dealer
10, and you lost both hands.

8. This double loss required you to place a bet of $2,880, which was higher than the $2,000 table max. So you bet the max, and lost.

9. On your next hand, you bet the max again, and insured your 20 vs. the dealer ace. You lost both the insurance bet, and your hand when the dealer hit to 21. This put you behind by a total of $7,880.

10. You then bet the max, and pushed.
11. You then bet the max and won!

You say that the above series of results took about 10 minutes, and that you do not recall the exact series of wins and losses in the approximately two-dozen hands that you played over the next 20 minutes. You note there were a few wins interspersed with the losses, but you had to have had 12 more max bet losses than wins (perhaps 18 losses and 6 wins?), as you left the table a $29,980 loser.
How "impossible" is this?
Unfortunately, not very.
You must realize that you were required to start placing max bets after only seven consecutive losses.

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