The African striker has failed to agree personal terms with the Championship club but has refused to rule out a transfer in the January transfer window
The 24-year-old was taken to a hotel in Oporto after Academica's goalless draw at Rio Ave on Saturday to discuss his transfer to Upton Park.
After the meeting, however, Eder disappeared with no explanation, which made the Portuguese club report the case to the police.
The Bissau-Guinean player has now explained the situation, telling Radio Renascenca: "I did not flee or disappear. I am in Lisbon with my family.
"We had a meeting at the hotel, but I did not like the way things were handled and I thought it was not the best for my career. I decided to leave."
Meanwhile, Goal.com Germany has learned that Koln are also in the race for the striker, who has been at Academica since 2008.
Questioned about his future on Saturday, Eder admitted that a move away from the Portuguese club is possible.
"I do not know if this was my last game, there are some days left [in the January transfer window], we will see what happens.
"I will decide what to do these days. I am not sure yet."