It sounds like your remaining right thyroid lobe is enlarged, but no nodules, and normal echogenicity. As long as it continues to not have suspicious nodules, you are probably ok keeping that remaining thyroid lobe, and that is good, because it is still producing thyroid hormone for you.
Some people do perfectly fine with only one thyroid lobe. Other people, including me (for the two months before the rest of my thyroid came out) struggle to make enough thyroid hormone.
Hopefully your doctor will check your thyroid hormone levels including free T3 and free T4 as well as TSH to make sure you are still producing enough thyroid hormone. Even with your thyroid still producing some hormone, you may need to take some supplemental thyroid hormone to make up the difference. If your thyroid hormone levels are too low, you might notice hypothyroidism symptoms including fatigue and weight gain.
My doctor checked my levels at about 1 month after my right thyroid lobectomy, and my TSH was already elevated (before my second thyroid surgery) so she started me on a low dose of levothyroxine (synthetic T4).
Good luck, and I hope you are doing well post surgery.