Sawsbuck generally leave their young in safe areas for hours on end, actually, and if your houndoom have done nothing to harm the local wild pokémon, it’s possible that the sawsbuck still view your yard as a safe place to leave their young. It’s important to keep in mind that most of the time, young deerling are left behind so sawsbuck can journey into more dangerous areas to forage for food without having to worry about their young being picked off by predators (trainers included). You won’t normally see the mother sawsbuck until much later, after the sun has fallen and the area has gotten dark enough to move the deerling without being seen. In some cases, you may think the deerling has been left for over a day, but in actuality, the sawsbuck simply retrieved their young in the dark and left them again shortly before sunrise, when they’re far harder to spot by human eyes.
You’ll know if the deerling has been abandoned, however, if you see signs of orphaning, such as a dead sawsbuck by the road or in the forest. (Sawsbuck with young that can’t fend for themselves will do anything they can to avoid being captured by trainers, but it’s worth it to keep an eye out for visitors with a new sawsbuck on their team as well.) Alternatively, you can watch during the night for any sign of movement, and if, after a week, you still have not seen the slightest hint that the deerling are being moved, then it’s possible that they’ve been orphaned.
In the meantime, yes, keep your houndoom away from the deerling as much as possible. Otherwise, try to avoid interacting with the deerling unless you’ve spotted the above mentioned signs. Young deerling are rarely abandoned, and the last thing you’ll want to do is accidentally cause one to attach itself to you while its mother is gone.