Steve76,
Blown off the bubble maybe not, but that horrid sinking feeling certainly is real when you accelerate from the rearwind condition (lots of good hover performance because that rotor doesn't care which direction the wind is from, mostly). As you get to groundspeed that is equal to wind speed, you are now at zero airspeed, the highest power point, and you had better have enough power. This is where the takeoff really starts, but you have spent hundreds of feet just getting here! Then you accelerate in airspeed and things get better again.
Bad takeoff technique if you are marginal in power, for sure! Not impossible, but not wise unless you really have to do it.