He felt that something was missing so he closed his eyes and tried to recreate that dream he experienced.
By the next morning, Sierra didn't feel quite bad anymore. That might have been because she has been spending her last days on the roof or staying at home, returning to her usual lifestyle and comfort zone. However, everything was a mess of her plans and he was in her mind constantly, there was no Elijah to push him out of her mind, there was no way she would imagine Elijah as him anymore and change her thoughts after that… But it was somehow the best outcome since she couldn't just keep thinking Elijah was him since that day he tried acting like him.