Yes, a transaction not reported on a 1099 form can be taxable. Generally, when a crypto asset is acquired and subsequently disposed of (through sale, payment of goods/services, fee payments, and other such events) it triggers a taxable event. Transactions of these types will likely not be captured in a 1099 Form.
Per the IRS, taxable events should be reported. Read more here.
NOTE: Lukka does not provide tax advice. The statements above are general in nature and do not address how the application of the tax rules can vary based on a taxpayer’s actual facts. Please consult a tax professional on how the tax rules apply to your specific facts.