can't really say. you say you have no documents to prove your loss. if you take it on your tax return and are audited, the IRS has the power to disallow the loss because you can't document it.
however, certain crypto exchanges report to the IRS through either a 1099-K or 1099-B. if you get them and they show the profit/loss that would be adequate if audited.
3 ways the IRS may find out about your crypto holdings.
1099-K & 1099-B. without any doubt, the IRS knows that you have reportable crypto transactions. This is thanks to the “matching” mechanism embedded in the IRS Information Reporting Program (IRP). Here is how it works.
During any tax year, if you have more than $20,000 proceeds and 200 transactions in a crypto exchange, you will get a Form 1099-K indicating proceeds for each month. The exchanges are required to create these forms for the users who meet the criteria. A copy of this form is provided to the account holder, and another copy goes to the IRS. If you file a tax return and do not include these amounts, the IRS computer system (Automated Underreporter (AUR)) automatically flags those tax returns for under reporting. This is how you get tax notices like CP2000. If you receive a Form 1099-B and do not report it, the same principles apply.
subpoenas
Over the past few years, the IRS has issued subpoenas to several crypto exchanges ordering them to disclose some user accounts. For example, in 2018, Coinbase - full a/c holder info pursuant to John Doe summons. On another occasion, Bitstamp was ordered to release more information about a taxpayer who filed an amended return and requesting a refund.
Schedule 1 Virtual Currency Question
Starting 2020 tax season, on Schedule 1, every taxpayer has to answer at any time during the year whether you receive, sell, send, exchange, or otherwise acquire any financial interest in any virtual currency (Cryptocurrency question). This is an extremely broad question and will require you to check “yes” even if you are just holding crypto in an exchange or wallet. If you mark “yes”, first & foremost, it would signal the IRS to check various forms & schedules of the return for cryptocurrency gains & losses. However, everyone who marks “yes” may not have a reportable taxable event. For example, during 2019, if you just held bitcoin and did not sell, you would not have any taxable amount to report. In these cases, the IRS will use the cryptocurrency question as a way to gather data about US crypto holders and keep an eye on future years for taxable events
