O.K. Everyone, here is the results of my research...first let me say it was a real hardship

watching that scene over and over again

BUT I did it just for ya'all in the interest of information.
I listened with the StereoTV at full blast, then again with headphones, then just the right speaker, then just the left

all the while looking at poor Heath looking so damn hot, uhmm I mean forelorn...

..and guess what... HE does NOT say I love you, he doesn't SAY anything.
There is a sharp intake of breath when he first discovers the shirts and sees the blood and realizes what it is, then a sigh when he see's how Jack has carefully preserved his shirt inside his own. Then another catch of breath and a sigh when you see the realization that Jack was in love with him dawn on his beautiful face and he clutches the shirts to his chest, inhales Jack's scent from them and sighs again.

By the time he comes back down the stairs he eyes are red rimmed from weeping. All the more poignant when you think of Ennis's discovering all this about Jack and how he felt about him, after listening to that old crumdgeon Mr Twist talk about some other guy and the obivious pain on Ennis's handsome face while he listened. And the expressions on Mrs Twist's careworn face...she knows, she knows it all from the minute Ennis arrives until he leaves.
Beautiful, beautiful scene but anyone who hears him whisper "I love you" or "I loved you" is wishful thinking. Part of the beauty and the tragedy of this story is Ennis's inability to utter those words. I personally am relieved to discover they are NOT there.