I was at -3000, Y, -3000 on a realms amplified server. I was visiting a friend, and was climbing a large hill to get to a nether portal to go home (we have nether hubs – none of our portals are near one another in the nether; and none were within 100 blocks of his). I remembered that I had ender pearls, so I threw one to a spot I assumed that would land right in front of said portal. I missed, and I assumed (like what has happened before) that nothing would happen, or if I went through the portal fast enough (which wasn't possible from my distance) that I may teleport once in the nether to where ever the ender pearl hit. Instead, my games FPS dropped to 3, and for about 4 seconds everything was blue (same thing that can happen when you TP to a new chunk). Suddenly I was suffocating in a wall. I dug myself a space to breathe, and tried to tunnel my way out (I assumed I got stuck in a block because of a bug). Suddenly I realize that I'm in a completely new biome (a mesa from a savanna). I check my coordinates and I'm at 400, Y, 400 roughly. I made my way to the 'spawn' nether portal and got home, but what the hell just happened? This has never happened before, and I have accidently thrown a ender pearl into a portal about twice. My bed was/is not corrupted, and said coordinates are not the spawn point that was set by the realms owner, and that has been where I have spawned if my bed was destroyed.

Note: 400, Y, 400 is about 600 blocks away from the set world spawn, and about 400 from the center of the spawn chunks on this server. I was between 30-70 blocks from the portal, and the portal was about 4 blocks above my Y. There was terrain behind the portal, a very gradual hill, and the next Y block up (that was behind the portal) was about 6 X blocks away. Hope that helps.