Ireland striker Long was given permission to leave the national team's training camp to discuss a "transfer-related matter".
The 26-year-old was reportedly at the Tigers' training ground when it emerged Baggies boss Steve Clarke had pulled the plug on the deal.
Subsequent newspaper reports have claimed Albion pulled out after Chelsea forward Lukaku - who spent last season on loan at The Hawthorns and had been linked with a return - had agreed a season-long loan at Goodison Park.
But Albion sporting and technical director Richard Garlick insisted that was not the case, claiming the move fell through because of Hull's proposed payment terms.
"Hull unexpectedly contacted us on Monday and tabled an acceptable offer for Shane. Given that every player has his price, we discussed it as a club," he said in a statement.
"We accepted Hull's offer in principle and gave them permission to speak to Shane, but the deal depended on many other factors - including a real reluctance to sell.
"In a phone conversation with Shane's representative, I informed him that Shane was under no pressure to leave. We were definitely not trying to force him out.
"Hull then informed us they could not finance the deal they had tabled and wanted to reduce it to a level that the club would never have accepted in the first place.
"Given that Shane was not a player we were looking to sell, we ended all negotiations with Hull there and then.
- Sports & Recreation