If one was davening SE without a siddur, and as a result he skipped a phrase or a sentence in one of the brachos of SE, but he said the bracha correctly otherwise, is he yotzi? How do we determine which phrases [besides the chasima] are me’akev?
Here are the Halachos regarding if someone skipped a part of Shona Esrei;
If someone forgot a whole bracha accidently or even just the ending of the bracha and he already started the next bracha, he has to go back to that bracha and continue davening from there, if this happened in the first three brachos, then he starts again. In the last three brachos he has to start again from Ritzay. If he already finished davening he has to daven again. (If he didn’t say the bracha purposefully he always has to start shmona esrei again). (O:CH 114-8, B:H ibid D:H Aval)
If he forgot a part of a bracha, whether it is a main part of the bracha, or not; if he is still in middle of that bracha, he should go back to that part of the bracha (M”B 119-14). If he already finished saying the bracha, he should insert it in shema koleinu, and if he didn’t insert it there he may continue saying shmona esrei. The reason for this is because even if he forgot to say the main words of the bracha, it will usually be said in the closing of the bracha, for example we say “kibutz galios” in the words “mekabetz nidchei”. However if he missed something that is not included in the end of the bracha, such as “V’sayn tal u’matar”, if he forgot it totally, he has to go back because it isn’t included in the closing of the bracha.
Also if someone forgot to say “mashiv horuach..” it can’t be said in shema koleinu since it isn’t a request, rather a praise, therefore it can’t be made up in shema koleinu. ( M”B 117-16)
Regarding saying the missed part of the bracha in Shema Koleinu see Siman 119-3 M”B ibid 13, 14 B”H D”H Im dileg, B”H 117-5 D”H im lo, B”H 59-2 D”H Vlo Amar, that we can rely on saying the part of the bracha that was missed in shema koleinu, and that we can rely on the opinion of the Gra that if the end of the bracha was good that it is alright. There may be other opinions; I wrote according to the opinion of Eishei Yisroel chap. 32-25, and ftnt. 97.