That IS very odd and I'm afraid I have no idea what you may have experienced. If you were not bleeding anywhere in your mouth or nose, then it had to be either the shampoo or the water. If your water comes from a well, it's possible the iron taste could have come from that or maybe the pipes. (Iron can taste like blood) Have you noticed this taste since you showered? Is the shampoo your normal brand? I would check your water to see if the taste is coming from there, then I'd take a VERY small dab of shampoo, mix it with the water and put a little on your tongue to see if you get the same results. If you do, then you've found the answer, or part of it. Use a different shampoo and see if that eliminates the problem. If it doesn't and you still get the iron taste, then we're looking at your water or your pipes. I hope you have a friend who is a plumber! Ask other people to taste your water. Talk to neighbors to see if they have noticed anything odd. You can also have your water tested by the county. Does your water have any discoloration to it? The only other possibility I can think of is if you're taking a new medication.........some meds can affect our taste buds. If none of the things I've offered up have any affect and you continue to have this problem, you need to contact your utility company and let them know something is wrong. If you're on a well, get your water tested. This may sound paranoid, but if I were you, I'd use only bottled water for drinking and cooking until this issue was cleared up.
Sorry I couldn't be of more help and I do wish you luck.