Hales's exit was the start of a slump that saw England lose three wickets for four runs as 64 for one soon became 68 for four.
Captain Carlos Brathwaite (3-20) and Kesrick Williams (3-35) then undermined England's comeback.
Chris Gayle, who returned to global cricket against India in July having not played for Windies since the final of that 2016 World T20, has been included in the tourists' squad.
Brathwaite ignited the collapse when he had Hales clean bowled off a straight delivery, then Joe Root (17) caught in the next over off Ashley Nurse.
Team News, England: England have two spinners in their squad - Adil Rashid and Liam Dawson - but will likely play just one given the expected conditions.
"Losing the game was losing three wickets in that period", said Morgan.
The Riverside, which has hosted 26 worldwide fixtures since being opened in 1995, was recently barred from hosting Test matches following a financial bail-out from the European Central Bank that also resulted in the club losing its first-division status.
Pakistan won the deciding third Twenty20 global against a World XI by 33 runs to ensure celebrations in Lahore.
Led by openers Chris Gayle (40) and Evin Lewis (51), West Indies got off to a ferocious start with the destructive Gayle bludgeoning four sixes before he was run out.
Tamim Iqbal fell after a rapid start to the World XI's reply and two wickets in successive balls in the fifth over had them in trouble, including Hashim Amla run out for a quick 21 after a mix-up with South Africa colleague Faf d u Plessis - who went the same way after Shadab Khan's direct hit to leave his side 67 for five.
Adil Rashid (3-25) and Liam Plunkett (2-27) put the brakes on West Indies' run spree once Gayle was run out in the seventh over.
That match saw fellow left-hander Lewis make a stunning 125 not out.
'I completely understand the frustration but there is certainly a huge need for guys who play all three formats to take a rest when needed, ' he said.
A rematch between the pair would have provided some much-needed context for a stand-alone fixture that could be seen as little more than a palate-cleanser between the Test and one-day global courses.