I'm not sure Ennis didn't come back down for supper the night after TS1, though it's plausible that he didn't and that would have made for a rather awkward meal, I'm afraid. I imagine Ennis spent at least a couple of nights with the sheep--like he was supposed to--after he found that sheep killed by the coyote, before he spent the night in the main camp again, and went into the tent with Jack.
This is a setting I
could imagine (although I'm not convinced of it): That Ennis came back only for awkward supper, maybe skipped breakfast and took some bisquites instead - in short: that he did what his job was: eat supper (and breakfast, or maybe skipped breakfast) in camp, but stayed with the sheep, for the rest of the time.
What I can't believe is that Ennis just did
not appear for supper the night after TS1, without any possibility to let Jack know. No mobile phones up there
. Remember how concerned Jack was when Ennis was just a couple of hours late after Ennis came on a bear? No way Jack would have waited one and a half day or even longer without any sign of life from Ennis. They were at the wilderness out there, there were dangers like bears or whatever. They had to rely on each other and to back up each other. If Ennis hadn't come back for supper the next evening after TS1, and additionally hadn't come for breakfast the next morning - Jack would not have waited till afternoon to go up and check on Ennis. Unattached from their relationship it would have been careless, even if Ennis had been a total stranger to him.
Another thing comes to my mind; Annie Proulx' essay in the STS book:
In such isolated, high country, away from opprobrious comment and watchfulk eyes, I thought it would be plausible for the characters to get into a sexual situation. That's nothing new or out of the ordinary; livestock workers have a blunt and full understanding of the sexual behaviours of men and beast. High lonesome situation, a couple of guys, - expediency sometimes rules and nobody needs to talk about it and that's how it is. One old sheep rancher, dead now, used to say he always sent up two men to tend the sheep "so's if they get lonesome they can poke each other." [...] The complicatin factor was that they both fell into once-in-a-lifetime love.So sure a big deal for our homophobe Ennis, with his history - but maybe not *that* earth-shattering. Ennis was pretty free and uninhibited with Jack their first summer. The total effect of his internal homophobia only set in once they came down the mountain, back into society, into the "real" world.
Ennis indeed needed time alone to mull over TS1. But I believe he managed in one day.
In the light of Annie's above quote, Ennis' words in the ain't queer dialog, seem almost natural: "This is a one shot thing we got goin' on here" (=one summer, and only sex, not in love, therefore not queer) - not: It
was a one shot thing, period (=only the one night).