Appleton says Liverpool haven't returned since having their opening bid for the winger turned down.
After their draw with Fulham, Appleton said: "Thomas played OK. He is going through an indifferent period because of all the speculation but he is coping really well.
"I am sure that once the speculation settles down, his performances will pick up.
"Liverpool made an offer two weeks ago but we have not received anything since.
"It was a case of 'That's not enough. You'll have to do better if you want him.'"