A brokerage firm has a few key jobs. One involves holding assets for clients and keeping track of who owns what.

FalconX, a cryptocurrency prime brokerage, apparently failed to do that for years with a pile of 1.35 million solana (SOL) tokens, now worth about $190 million, that it’d had in its possession since 2021.

Then, Binance, the largest crypto exchange and a key liquidity partner of FalconX, recently came forward as the rightful owner and asked for its SOL back.

It’s unclear exactly how FalconX was unable to keep track of the crypto and how Binance itself seems to have lost track of the money for years. But the situation raises questions about accounting systems and controls.

Around the time the trove of mystery SOL appeared in FalconX’s coffers, the value of the tokens lingered at around $20 to $30; not long after the collapse of FTX in late 2022, SOL sank under $10. At those prices, even 1.35 million Solana tokens are chump change to Binance, which has over $110 billion of assets in reserve and services over 90 million customers worldwide.

FalconX, when contacted by CoinDesk, confirmed that there had been “a reconciliation anomaly” involving solana tokens. The company reconciled its books against all exchanges, clients and partners, and no one showed records of a transaction, according to a FalconX spokesperson.

Binance, when contacted by CoinDesk, said its customers were never at risk of losing money as a result of the situation. Binance would’ve simply absorbed the loss itself if the 1.35 million tokens had never been found.

To earn money on the assets they’re in charge of hanging onto, prime brokerage firms like FalconX typically put assets to work, using them as collateral, or for lending or arbitrage opportunities. But that did not happen in this case as the assets were held in safekeeping, a FalconX spokesperson said.

Not long after CoinDesk came asking questions about the lost and found solana tokens, the companies responded via a joint statement, saying the assets in question were being returned to Binance and that the matter was now fully resolved.

“Binance and FalconX continue to operate business as usual,” the firms said in an email.

Mysterious transactions and reconciliation head-scratchers happen in traditional finance, too, but crypto could be uniquely prone to a situation of this sort, where assets go unclaimed for years, inflating hugely in value in that time. Of course, crypto is a new area of finance, running on rapidly evolving infrastructure, which is home to highly volatile assets.

Speaking broadly, big auditing firms like PwC agree the relatively young crypto space is potentially susceptible to such reconciliation issues. “Mainly I would say the unregulated space is where things are less mature and there is a weaker control environment,” said Peter Brewin, a partner at PwC Hong Kong who specializes in digital assets, Web3 and the metaverse with a focus on tax and regulation.

FalconX, which was established in 2018 and valued at $8 billion at the time of a mid-2022 funding round, offers institutional customers a dashboard to manage portfolios and connect to a range of crypto exchanges, custodians, market makers and prop shops. Altogether, the brokerage handles over 100 million transactions a month, using a complex system of omnibus and subaccounts.

Binance recently made a move to close a VIP fees loophole used by prime brokerage firms, citing a lack of transparency in the way these firms structure their client accounts.

In the wake of FTX’s collapse, crypto trading firms have been focused on keeping critical functions in safely segregated structures, as Anatoly Crachilov, CEO and founding partner of Nickel Digital Asset Management, points out.

“Trading venues running matching engines do not hold assets, while custodians safeguard client assets, with market value further validated and reported by an independent fund administrator,” Crachilov said in an email.