This week I attended a family yartziet siyum seudah and the discussion arose whether someone who missed the actual siyum could eat the meat at the seudah. Someone pointed out a Chayei Adam quoted by the Mishna Berura that says you can not send food from the seudah to someones house. This person wanted to prove from here that you need to hear the siyum. L'aniyas da'ati I am not convinced it is a good rayah, since it is not clear to me what exactly is the point of the Chayei Adam. He could be saying that you have to be present at the siyum but he could also be saying that the food doesn't fall into the catagory of eating at a seudas mitzvah unless you are present at the actual meal. Especially during the nine days when there is a hakpadah to only invite friends and relatives, it could be the Chayei Adam feels to send the food to a person is not good enough. To me it is a tzarach iyun on how to understand the implications of this Chayei Adam.
I did look in the Pischei Teshuvos and he directs you to the siman on Ta'anis Bechorim. Although maybe one can be m'chaleik between the siyum of 9 days and the siyum of ta'anis bechorim, the Piskei Teshuvos obviously feels you can equate the two. The pashtus would be to equate the two cases since the heterim of both revolve around the idea that you are eating at a seudas mitzvah. If by ta'anis bechorim eating at the seudah even though you missed the siyum is allowed because al kol panim it is still a seudas mitzvah so too it should be the same thing by the 9 days.
In any event, by Ta'anis Bechorim he brings a machlokes haposkim whether one has to be at the siyum or is just being at the seudas mitzvah enough.
The Minchas Yitzchak in cheleik 9 siman 45 says by Ta'anis Bechorim if you missed the siyum you can still eat at the seudah. His rayah is from a Biur Halacha in 551:10 which deals with the halachos of the 9 days. Clearly, from the fact the Minchas Yitzchak brings a rayah from the 9 days to ta'anis bechorim he holds that in both cases one does not have to be at the siyum.
I did not get a chance to look at the other mareh m'komos brought in the Piskei Teshuvos and nor is it clear to me if the other matirim by Ta'anis Bechorim would also be matir by the 9 days.
Eating before the siyum
The other question that arose is whether one can eat the meat before the siyum takes place or must one wait for the siyum. L'mashel if one washes and eats bread before the siyum must you wait for the siyum before eating the meat or can you eat the meat right away. I think one can say it depends on what gives the seudah a shem "seudas mitzvah". Is it the potential siyum that will take place or is it like kiddush on Shabbos where the kiddush is koveia the seudah as a seudas Shabbos (acc to one approach in kiddush). I once asked a poseik by any siyum can one wash before the siyum and still be considered as eating a seudas mitzvah or must one wait for the siyum in order to call the meal a seudas mitzvah. He told me (if I remembr correctly) that one can wash before the siyum and it is stil a seudas mitzvah. If that is case maybe we can apply the same sevarah here too and say that you can eat the meat before the actual siyum took place. (although what would happen if the siyum wound up never happening-do we say l'mafreia you ate meat b'issur during the 9 days).