Em and Sid are not to blame. They are not the people who decide if they have to stay or leave. They still there because their managers are ok with them being there.
About Sid, i remind people that he came back on tuesday. The same day Lisa and Grant came back, the same day Kyle came back, the same day Misty came back. Is that a coincidence? I don't think so.
The day Sid "left", he had a backpack and looked more like someone who was taking some days off than a guy who was leaving for good. For me, he has never left.
About Em, what i understood from Groomy when he said Em had a test until 10-11 may, is that he was talking about a school test (maybe i'm wrong) and not about a probation or an ultimatum for Em.