I saw the thread on Hyatts, that were announced and never got built... thought it would be nice to have a thread on Hotels, which left the Hyatt group.

Here a couple of ones I can think of

Europe
HR Montreux, Switzerland - today: unsure (Royal Plaza or Fairmont?)
HR Brussels - today Hotel Barsey by Warwick
Hyatt the Lowndes (London) - today Jumeirah Lowndes Hotel
HR Budapest - today Sofitel Budapest Chain Bridge
HR Warsaw - today Regent Warsaw
HR Jerusalem - today Dan Jerusalem Hotel
PH Villa Magna Madrid - today Villa Magna
HR La Manga Resort (Murcia, Spain) - today La Manga Club

Africa

Hyatt Oubaai - today Oubaai Hotel Golf & Spa
GH Cairo - today Grand Nile Tower

Asia

Hyatt Saujana - Today "The Saujana Kuala Lumpur)
Hyatt Aryaduta - Today Hotel Aryaduta Jakarta
HR Hong Kong (pulled down and newly built)

Americas

U.N. PLaza (NYC) - Today I believe it's a Millennium hotel (One UN Plaza)
The Bonaventure (Weston) - today
Hyatt Cancun Caribe Villas and Resort - Today Grand Park Royal Cancun Caribe
HR Cancun - Today Krystal Grand
HR Hilton Head - today Hilton Head Marriott Resort & Spa
HR Lake Las Vegas - today Westin Lake Las Vegas Resort
HR Lincolnwood - torn down
The Victor (Miami Beach) - today Hotel Victor South Beach
Hyatt Miami at The Blue - today Provident Doral At The Blue
HR Grand Cayman - not built up after hurricane
HR St John, USVI - Today the Westin St. John Villas
HR St Lucia - unknown
HR Curacao Golf Resort, Spa and Marina - today Santa Barbara Resort