One-time pad mistake in the transmission?
Assuming that you have not used the one-time pad bits $k_2, ..., k_{N+1}$ to encrypt another message, then the answer is no, the attacker cannot determine the message.

This can be seen by using the normal proof of One Time Pad's security; the bits $k_2, ..., k_{N+1}$ are random and uncorrelated to any other bits the attacker has access to; hence the attacker gets no information on the values of $a_1, ..., a_N$ from the sequence $a_1+k_2, ..., a_N+k_{N+1}$.  That those random uncorrelated bits are not the precise ones that you intended to use is irrelevant.

On the other hand, if the sender realized his mistake, and then sent $a_1+k_1, a_2+k_2, ..., a_N+k_N$, at that point, the attacker could deduce information about the message.  This violates the restriction that "bits from the one time pad are used only once", and this actually allow the attacker to deduce the original message (or its complement).