What the halacha if someone is in middle of shemona esrei and spaces out and is completely unsure where he is holding? Does he go back to the the last bracha he remembers even though it was awhile and definitely went further
Someone in such a position is really in a tight spot. On one hand if he continues, and he really skipped some of the brachos it could be that what he is saying is a bracha lvatala, because the brachos have to be said in order. However on the other hand if he goes back and resays some brachos he might have already said them, and now he is saying a bracha lvatala. (The moral of the story is don’t space out!) The Chayei Adom (24-21) suggests that he continue from where he think he might be up to, (the further place) and continue from there. However most poskim ( see sources) disagree with this, and hold that if someone davened shemona esrei and doesn’t know where he is holding that he has to go back to the place that knows that he for sure said, and continue from there. It is true that he might have gone further, but as long as he doesn’t know, he can’t just continue, therefore he has to go back until where he is sure that he already said.
See Pischei Teshuva O:CH 119-3, see Kehilas Yackov (Brachos 17) who brings the Ohr Zarua siman 374(1), and a Yerushalmi (Brachos Ayn Omdim-3) that if one who doesn’t know where he is that he goes back to where he is sure that he already said. This is also the opinion of the Ben Ish Chai Parshas Mispatim-20, Kaf Hachayim 119-20 in the name of Chesed L’avrohom, Chazon Ish in Orchos Rabeinu 3-pg. 307 (old edition). It is interesting that the Mishna Berura does not bring the Chayei Adam but regarding one who forgot where he is up to in bentching, in siman 188-6 Biur Halacha D:H Lachzor he brings the Birkei Yosef that he has to go back to where he surely already said. See Pischei Teshuvos 119-5. Also see Minchas Yitzchok 5-100.