When attending a social event at work, a religious Jew with a long beard is approached by a non-religious Jew who says, “Please hold my plate while I quickly run to the men’s room.” One looks at the plate and sees that it is filled with shrimp and pork. Is it permissible for the religious Jew to hold this plate while the person goes to the bathroom and then to return it to him when he emerges from the bathroom? Is it an issue with maris ayis, not to mention other issues that may be involved with returning it to him? What is the appropriate response to such a request?
There are two potential issues with holding the plate for him. Firstly as you wrote there is an issue of maris ayin. It doesn’t look very good to be in public holding a plate of shrimp. For this you can make an announcement, that the shrimp is not your but you are holding it for someone else. However the other issue would be one of Lifnei Iver, or to be more exact “misayeya l’yidei ovdei aveira”, assisting someone to do a sin. When you give the man back his plate, you are essentially serving him the shrimp. You should put the plate down, an later on excuse yourself, and tell him that something came up, ( the realization that you are not allowed to hold the plate) and therefore you had to put his plate down.