You won't find anything (from a reliable source) about pheasants having a problem with chickens or chicken droppings. Peacocks and turkeys are the ones who can't cohabit with chickens or where chickens have lived until they are at least four months old. Even then it's not a good idea for turkeys.
Turkey and peacocks are highly susceptable to "blackhead"
Blackhead disease, or more correctly, histomoniasis, is primarily a disease of young turkeys. Chickens are more resistant to the effects of the infection but may act as carriers of the disease-causing organism. Histomoniasis is caused by a microscopic protozoan called Histomonas Meleagridis. The name blackhead is a poor descriptive term because the heads of the birds infected with this parasite are not dark. The protozoan causes considerable damage to the liver and ceca of infected turkeys, and the untreated birds usually die.
Since turkeys and peacocks are almost identical physiologically they are both susceptable to blackhead. The very few vets around who treat peacocks know that a peacock receives the same treatments as turkeys.
But histamonas generally pass through pheasants and chickens causing no ill effects, but they contaminate the ground with their droppings and the histomonas live in earthworms and the cecal worms can live in the ground for up to three years.
You can't put a pheasant chick in with adult chickens and be safe. If you had a chicken with baby chicks you could have done it the first day if the pheasant was only a day or two old. I have done that with no problems.
Your best bet is to hand raise it..