A case of doubt about 4 or five damages (five oxen for one ox and five sheep for one sheep ) is an argument between the Rambam and the Raavad. The argument is if the owner of the injured ox has grabbed the ox that caused the damage. To the Rambam [laws of theft 2. law 12] he can keep what he grabbed, but the Raavad has several questions on that. It is more than what he damaged, and there is a doubt so no court that has authority to decide. The answer to the first question,  Rav Shach suggests that only half damages we say if he grabbed  he can keep [which is an open gemara- a person that grabs half damages can keep it until the court convenes and decides the case ], but in our case of four or five damages not. 

so rav shach seems to be saying that  in our case  of 4 or 5 times the damage would the raavad hold you take away the ox if it has been grabbed==even if not a doubt. only if it is a case of half damages that you do not take away the grabbed object. i mean to say that rav shach does not refer to the aspect that our case is one of doubt.  

For some reason, Rav Isar Meltzer did not suggest this answer, but rather refers this subject to an argument between the Rosh and Rabbainu Yona in Ketuboth pg 20. [paragraph 13 in the Rosh]-

Also he mentioned to look at the Rosh in Bava Kama 15 [paragraph 20 in the Rosh]. The Rosh brings there Rav Meir HaLevi who held תופס חצי נזק אין מוציאים מידו ( We do not take half damages away from one who grabs them) except for 1/2 damages-- which would work fine here for the Raavad except for the fact that the Raavad elsewhere in the Rambam holds we do not take half damages away from one who grabs them in general. So Isar Meltzer says the Raavad holds only in a case of doubt do we take away the  half damages because it is like a guarantee for a loan. and in the case of doubt for a guarantee for a loan we would hold  we do not take  away from one who grabs them. But here its is a ''kenas'' punishment for the damages, not monetary.