I have employed a massive hack for the past two decades--whenever asked to do any random task or assist someone, and in particular where the asker is just lazy trying to get someone else to do their job, eagerly and pleasantly agree, but ask the requestor to write up a sentence or two describing said request and email it to you. It's such a small request that no one can't argue it, but so many people (lazy ones especially) are astonishingly bad at this and 90% of the time that request will never come. The next time you see the person, take the initiative and remind them about the email you never received and ask if they could send it. You've now turned the tables on the asker, they may even start to avoid you.