I didn't know what they could have forgotten so you can decide yourself what they forgot.

Tomura Shigaraki:

He heard Kurogiri say someone is here for him so he looked, expecting some idiot wishing to join, but it was you so he couldn't help but get a little smile before he asked why you are here. When you told him he forgot something, he groaned, not happy he forgot something before he took it from you, muttering a thanks.

Kurogiri:

When someone knocked on the bar door, he stared at it, wondering who would come here before he opened it, only to get a little shocked when he saw you, saying your name. When you held up the item he forgot, telling him he forgot it. He smiled, thanking you as he took it, telling you that you didn't have to go through all this trouble before he invited you in to have a drink.

Dabi:

He was walking out the bar when he saw you approaching so he walked to you, asking you why you are here. When you told him he forgot something, he glanced at the item you held before sighing, telling you not to come to this shitty place just to return something he forgot. He took it with a lazy "thank you" before he wrapped his arm around your shoulders, saying he finished with work so let's go drink something at a nearby cafe or bar.

Himiko Toga:

When she heard a knock on the door, she immediately recognized that knock and jumped off the bar counter and swung the door open, excitedly greeting you before giving you a tight hug then pulling you inside, asking why you are here. When you said you came to return something she forgot, she got a big grin, saying you are so kind before she took it, pushing you to the bar, telling Kurogiri to pour you a drink because you deserve it after walking all the way here to return something.