ריב"ח chose to use the expression of ר' יהודה that he wrote שם משמעון (even though one would be liable for just marking [according to ר' יוסי]), since that expression is clearly written in the משנה
What is the ruling if he is unaware of this and this - העלם זה וזה בידו מהו
העלם זה וזה includes a case where he is unaware of any איסור מלאכות, provided that when reminded he remembers; otherwise he is considered a שוכח עיקר שבת and is only חייב one קרבן (even for many שבתים).
We see; if he refrained because of שבת, etc. - חזינן אי משום שבת קא פריש כולי
רש"י maintains that אי משום שבת קפריש means that he was informed that it is שבת (and similarly אי משום מלאכות, that he was informed that these are מלאכות). The ר"י maintains that it depends on which was more forgotten שבת (one) or מלאכות (many). However רב אשי has no resolution if they were equally שכוח. The רשב"א maintains that if they were equally שכוח (according to רב אשי) he is חייב for each מלאכה.