I lost like this in a no limit Texas Holden game at full tilt like 6 years ago.......it was a $500 entry fee & I had knocked out 2 players after only 2 deals & I had the high stack in the tourney .........next 2 deals I got clocked.
I got dealt a flush on the flop & I go all in & the guy that calls gets runner runner & beats me with a full house......there goes half my stack.
Next deal, I flop a straight, guy beats me with runner runner for a flush which knocks me out cause I went all in.
My cousin was watching me play from his house & he called me & said that it had to be rigged somehow.......lol!
That's the last time I ever played online poker becausebi think its very shady. I played on party poker before full tilt & I thought it was a way better site.
I don't recommend online poker to anyone.......its been proven time & time again that it has been rigged in certain situations.
Every facet of gambling has a shady side.......whether its the refs cheating in a game, a jockey holding back a horse, etc......
As for could your opponent see the cards? Its possible with expensive & sophisticated software & since these sports books are not known for their poker, I doubt they have great protection against someone infiltrating their poker pages (only making an assumption)
Let's not forget, there are lots of unorthodox poker players out there that don't follow the supposed way we think we should all play, & maybe that's all that happened when your opponent called you......