As for the sentence in question, キャラデザのラフを見た is about the state of their work, the latter half of the sentence implies that the advance of the production is quicker than the speaker expected.
Generally, X(だ)と思ったらY means the time between X and Y is shorter than expected. As such, the time is not under the control of the speaker. That should explain why 私はうちに帰ったと思うとまた出かけた is odd. The speaker decided to go out her/himself, so there should be no surprise as regards the time span.
Probably the rule for the non-applicability of the construction should be something along the lines of Y not being the speaker's voluntary action.
As an example, the following is possible:
- I just came back to Japan a short while ago, and I have to go to the USA next month.
Here Y is not the speaker's action but the situation where s/he has to go to the US, and staying in Japan for a few months is shorter than the speaker expected.