Strict liability offense means even mistake of the fact can not be a legal defense. An example is speeding, you cannot say you are not watching the odometer so you were not aware that you were driving 10 mph aboive the limit. But whether
the offense is trict liability or not, ignorance of law is never legal defense you can only use ignorance of law to argue
for some lenience.
It is understandable that laws should not allow ignorance of law to be used as legal defense otherwise everyone would
try hard to make himself as ignorance as possible to avoid legal punishment.
WBH, please re-read my post. Where do I even mention "ignorance of the law"? I said OP is safe if his failure to file an AR-11 is not knowing and willful. Willful means deliberate or on purpose or intentional and not just merely negligent.
Therefore, if it was not on purpose, there is no liability for the failure to file.
I base my opinion from USCIS apparent interpretation of 8 USC 1305 and 1306. From the USCIS website at http://ow.ly/1gCei:
Penalties for Failure to Comply
A willful failure to give written notice to the USCIS of a change of address within 10 days of the change is a misdemeanor crime. If convicted, the alien (or parent or legal guardian of an alien under age 14 who is required to give notice) can be fined up to $200 or imprisoned up to 30 days, or both. The alien may also be subject to removal from the United States. (INA § 266(b)). Compliance with the requirement to notify the USCIS of any address changes is also a condition of an alien’s stay in the United States. Failure to comply could also jeopardize the alien’s ability to obtain a future visa or other immigration benefit.
OP said he thought he filed by mail but was unsure so he filed online. Does that sound like he failed to file on purpose? Or do you think USCIS interpretation is misleading?