יכול יעצים עיניו כמי שלא ראהו ת"ל תקום ויראת דבר המסור ללב נאמר בו (ויקרא יט, יד) ויראת מאלהיך
I might have thought he can close his eyes like one who did not see [the elder]; the Passuk teaches, “You will get up and fear [your G-d]” (Vayikra 19:14); anything given to the heart, it is said by it, “And you will fear your G-d.”
Anything? What about Hashavas Aveidah, where the same argument can be made: I might have thought I can hide my eyes as if I didn’t see the lost object and thereby exempt myself from having to return it; yet the passuk never says “fear your G-d” by returning a lost object, neither in Shemos 23:4 nor in Devarim 22:1-4. Why? Likewise aiding a struggling animal (Shemos 23:5), nor helping to load an animal (Devarim 22:5), nor Shiluach HaKan (Devarim 22:6-7), nor countless other mitzvos by which one who does not see the object is exempt - none of them say “you will fear your G-d” as a warning that you shouldn’t pretend like you didn’t see it.
I suppose this question can be asked in two ways: how can the Gemara say that “you will fear your G-d” is said by anything given to the heart, when we see it’s not? Alternatively, what is unique about standing for an elder which warrants this phrase to be used in this manner?